I will try to avoid the indigestible soup of putting everything in the same pot, and curb my frame of reflexion to the mere components of your question - sticking as much as I can, to the fields of sense (ayatana) :
“When the six sense fields fade away and cease with nothing left over” is this via jhānas ?”, you ask.
The original question in SN 12.2 is:
Venerable sir, who makes contact?”
“Not a valid question,” the Blessed One replied. “I do not say, ‘One makes contact.’…
… I do not speak thus. Since I do not speak thus, if one should ask me, ‘Venerable sir, with what as
condition does contact come to be?’ this would be a valid question. To this the valid answer is: ‘With the six internal fields of sensory experience as condition, contact comes to be;
with contact as condition, feeling.’”
Contact through the eye, ear, nose, tongue, body, and mind.
(the six internal fields of sensory experience).
One does not make contact.
It is with the six internal fields of sensory experience, as condition, that contact comes to be.
What are these six internal fields of sensory experience (ajjhatikkani ayatanani) ?
Read this first: SENSE-EXPERIENCE in Genuine Buddhism ( from Texts common to Early Buddhist schools ) ________ .... - JustPaste.it
Then the notes on ayatana at the bottom of this page: * - JustPaste.it
Now, what is said about jhana’s requirement ?
Jhāna (from jhāyati) - Sanskrit: kṣāyati, from √ क्षि kṣi - to make an end of (RV. AV. MBh.)
See jhana- JHANA (All the Suttas’ extracts below, have parallels in Chinese, and/or Tibetan, and/or Sanskri... - JustPaste.it
The first jhana is, among other things, about making an end of the sensual pleasure, through seclusion (vivicceva kāmehi).
See Viveka - VIVEKA Discrimination / Separation / Seclusion ________ . Note: Viveka has always had the meani... - JustPaste.it).
Viveka is discrimination between the external and the internal - separation from the external - and seclusion in the internal.
This is a requirement, and the process as well, of the first jhana.
One doesn’t need to cross legs and do the all shebang of “deep absorption” to do jhana, at this level.
One should just restrain the indriya(ni). That is how one perfects and completes the seclusion (viveka) . This is how the six internal fields of sensory experience come to fade away.
However, in your question, it is said that “the six internal fields of senses should also” cease with nothing left over".
Going back to the link provided above on jhana, you can see that this does happen in the fifth jhana. (explained here * - JustPaste.it - in blue at the bottom of the page - Note also that, in previous threads, I have already suggested that perception/sanna has also the underlying meaning of “inquiry and its assumptions”, in the Vedic texts).
Simple, isn’t it ?
Maybe a bit hard to understand within a Lockean or Humean frame of mind. But not for Kantian or Cartesian ones, for instance.
In other words, you can advance (or retreat and escape, ) through non-sensory spheres (in higher jhanas). For everything is not just senses in Buddhism; as in Descartes, Kant, Hegel, etc…