Venerable Vimalaramsi’s teachings contains a lot of idiosyncrasies. That dukkha is a tightening of the meninges, and so to deal with dukkha/hindrances you have to relax is one of them.
Furthermore , Ch’an/Zen contains within it a heavy emphasis on “broad awareness” type meditations like shikantaza , simply directly observing the mind, and is, in fact, the oldest living Buddhist meditation tradition in the world, having records of lineage going back all the way to Bodhidharma and then the Buddha himself. My guess is that the majority of arahants throughout time have been Ch’an masters, partially because the Ch’an/Zen tradition is so old and had such laser-focus on meditation and Awakening-in-this-life for its entire history, but primarily just because of demographics. Ch’an/Zen has stuff like koans, “just sitting”, broad awareness qigong energy manipulation, you name it. They really went to town with meditation and experimented with everything.
Shikantaza is simply sitting, whilst the Buddha taught a more active meditation with the breath or elements etc. You have to deal with the hindrances, not just observe them. Whilst Zen does make use of mindfulness of beathing, it is only as a pre-liminary. The early Zen however were heavily influenced by the Dārṣṭāntika, a Sautrāntika tradition. Whilst their view was that the sukha in Jhāna was bodily and so the 5 senses could occur, it still taught the idea of focusing at one point during meditation. For example,
Discourse on Higher Advancement (parākramaṇa-bhāgīya) in the Preparatory Path (prayoga-mārga)
5.1 Bhikṣus practising Ānāpānasmṛti will proceed to higher distinction (parākramaṇa-bhāgīya) in their spiritual cultivation if they have successfully abided in positive effects. Their prajñā will also be enhanced. I shall herewith expound it in orderly sequence.
5.2 Once having advanced after abiding in positive effects, the practitioner should, again, abide in positive effect. That is why it is essential for any practitioner to abide in positive effects for the sake of attaining higher distinction (parākramaṇa-bhāgīya) in his practice.
5.3 Meanwhile, he should always concentrate on his nose-tip, making his mind bind firmly there, focusing all his thoughts in the proper observation of the wind. He should then keep his in-breaths and out-breaths firmly in mind and follow them closely in his recollection (anusmaraṇa).
5.4 If he does that well without laxity, he has initially abided in positive effects. Once this has been achieved, then he should keep up his preparatory effort (prayoga-mārga) for further advancement.
5.5 Then the practitioner‘s quest for further benefit will bring about positive abiding, followed by higher distinction (parākramaṇa-bhāgīya). Furthermore, it should also be noted that higher distinction will simultaneously bring in the abiding in further positive effects. Hence, when one passes the positive abiding state and advances further, another abiding in positive effects will come forth.
5.6 Therefore, once the practitioner appreciates fully well the various patterns of ānāpāna (exhaling and inhaling) and their ensuing benefits (guṇa) and faults (doṣa),for instances, whether his breathing is light, or heavy, or cold, or warm, or delicate, or rough, or sticky and or smooth he will fully understand that the concentration on ānā (exhaling) which combines with that of apāna (inhaling), can maintain control over his faculties (indriya-s), with their cognitive objects (ālambana) quietened and subdued to tranquility (śamatha) and nirvāṇa.
5.7 Similarly, there is also a similar way to control the wandering thought-concomitants (caitta) by counting the breaths and focusing on how they enter the body. This, is the essence of ānāpāna (exhaling and inhaling) which stops one‘s thought from chasing the cognitive objects (ālambana-s) Even one‘s thought of the cognitive objects will also be extinguished by its control.
Dharmatrāta-dhyāna-sūtra
In the Zuòchán sān mēi jīng, another Dhyāna-sūtra, it says to to fix at any point from nose through to chest or navel
Question: Why?
Answer: To end thoughts and attentiveness so that the mind is not scattered. While following the breath and counting it, the mind is not stable because of the many disruptions to the mind. Quit counting and the mind is at leisure with little work; hence the mind is single-pointed while it is mindful of the in and out breath. For example, a guard stands by the door and observes the comings and goings of people. The mind at a stop is the same: it knows when the breath is exhaled, going from the navel to the chest, throat, then the mouth and nose. When the breath is inhaled, it moves from the nose and mouth to the throat, chest, and then the navel. By fixing the mind on one place, it is called “stopping.” Furthermore, residing in the method of stopping is contemplation. The coming into being and the ceasing to be of the Five Skandhas during inhalation is distinct; the coming into being and the ceasing to be of the Five Skandhas during exhalation is distinct. When the mind is scattered, the contemplation disappears. By contemplating singularly, contemplation grows, which is called the method of contemplation. By leaving behind the cruder method of contemplation and abandoning dwelling on the gates of the breath, you know that breaths are impermanent. This is called the Turning Contemplation. Contemplating that the Five Skandhas are impermanent, being mindful that the production and extinction of inhalations and exhalations are impermanent, seeing that the start of the first breath comes from nowhere, then contemplating that there is no trace after the breath in that breaths exist due to a combination of causes and conditions and disappear due to the dispersion of causes and conditions is called the method of Turning Contemplation
We also see in the Chán fǎ yào jiě the appearance of nimittas
Question: How can one recognize the signs of single-mindedness?
Answer: When the mind dwells on an image, the body would be soft, gentle, and blissful. All anger, anxiety, grief, and other afflictive mental dharmas are ceased.174 The mind acquires swift blissfulness never before experienced, which surpasses the five desires. Because the mind is pure without any defilement, the body will shine brightly. It is like a pure and clean mirror [shining] the light externally, or like the shining light of bright pearl that appears, illumines, and manifests in the pure water. After having seen these signs, the cultivator‘s mind is calm, tranquil, joyful, and delightful. It is like a thirsty person, who digs the earth searching for the water. If he sees the moist mud, then he will get the water soon. The cultivator practices in a similar way as such; at the beginning of the practice, it is like digging a dry earth for a longtime without stopping; as he sees the signs of moisture, he knows himself that he will get the water soon. Having known by oneself that one will attain the meditative samādhi soon, one must diligently concentrate, joyfully believe, gather the mind, and move it to enter the deep samādhi. Give rise to the thought that ―I have already cursed the five desires.‖ See those who seek after their desires as extremely detestable, as one sees a dog, who, unable to get good food, chews on stinking manure. According to these various conditions, you should curse desire as a fault. One‘s mind gives rise to sympathize with those who experience the five desires. Their own minds have blissfulness already, but they do not know how to seek for it. Instead, they seek for the external impurity and faulty joyfulness. Throughout day and night, the cultivator should always practice diligently various wholesome dharmas, which support the achievement of meditative samādhi.
Question: What are the marks of attaining the first dhyāna?
Answer: At first, one uses proper mindfulness to admonish and halt five desires. Although one has not attained the ground [of the first dhyāna], the mind is joyful, delightful, soft, harmonious, and gentle; the body has bright light. When one attains the first dhyāna, its mark is that it continuously changes, increases, and excels [than before]. Because the four elements of the Desire Realm spread fully all over the body, which is soft, harmonious, gentle, and joyful signs, and the mind leaves bad desire and unwholesome deed, then the samādhi of single-minded thought can cause one having joy and happiness.183 Forms created in the Form Realm have the feature of bright light. Hence, the cultivator sees the wonderful and bright light emitting from the body internally and externally. The mind of the cultivator changes differently. Within the angry situation, one does not get angry. Within the joyful situation, one does not have [much] joy. The eight kinds of worldly dharmas cannot move the cultivator.184 Faith, respect, shame, and conscience largely change and multiply. As for the clothes, food, and drink, one does not crave and attach to them. One only considers various wholesome deeds and meritorious morality as valuable, and others are worthless. One does not attach to even the five celestial desires, how much more the five impure desires of the secular world. For those who have attained the first dhyāna, these are the features.
You go on to say
Theravada just didn’t do very much meditation for a very long time, or at least not in an institutionalized, organic, dynamic, focused way like the Ch’an/Zen. The Dhamma has never been dead, it was just primarily being done in China rather than Sri Lanka. And that’s not even to say that it wasn’t ever being practiced in Sri Lanka, just that the Theravada meditation tradition very clearly ran out of steam and eventually died. Not exactly a healthy sign of success…
But this simply is not true. There has always been a meditative tradition in Theravāda, be it orthodox or esoteric. As for Zen, many of its practitioners ended up saying we are already awakened. That doesn’t look like a healthy sign of success to me. Of course, if you want to think all these meditation masters and meditative traditions just didn’t know what they were doing for 2000 odd years, until Western monks discovered the true way, you can.
I agree with Ceisiwr that it is pretty crazy to think that all this people in the past did practice incorrectly. Maybe they just found a little bit different way, but still within basic principles of Buddha-Dhamma, so working? 
