Let’s just acknowledge that.
However, as to the meaning of the suttas:
This quote from MN121 doesn’t say that bhava doesn’t exist anymore after enlightenment. It says that there is “no disturbances based on bhavāsava”. That’s different.
As I see it, it’s just an issue of interpretation of a single term. If we translate bhavāsava as “taint of being” then it sounds like bhava ceases at enlightenment. But that contradicts Iti44, as well as other suttas that say that enlightened beings are still in a state of bhava. For example AN5.170: "The state of existence (bhava) in which the defilements are ended without delay is the best state of existence.” Acording to this, the defilements (or ‘taints’, āsavas) can cease while there is still bhava.
Bhavāsava can also be read as “taint towards existence” instead of “taint of existence”. This so-called taint towards existence is the desire for existence, hence Ven Sujato translating bhavāsava at such. And as Bhikkhu Bodhi also notes at MN131 for bhavasamyojana, which he translates as “the fetter of being”, refers to “craving for existence”. That is, bhavasamyojana can be interpreted as “the fetter [that ties us] to being”. Similar for bhavāsava.
When we interpret these terms in this way, there are no inconsistencies with bhava still existing for the enlightened ones. Or how do you (or Ven. Ñāṇavīra) interpret Iti44 and AN5.170?
Either way, the meaning of bhava is a technicality. I don’t think it matters for the core question, because even MN121 you quoted says:
The sutta then says:
Thus he [the enlightened one] regards it [enlightenment] as void of what is not there [i.e. the “taints”], but as to what remains there [i.e. the six senses] he understands that which is present thus: ‘This is present.’
The six senses are intrinsically suffering, as said e.g. in SN35.2. And SN56.14 says the six senses are the noble truth of suffering.
So, while a big amount of suffering clearly ceases at enlightenment (at the cessation of taṇhā), not all of suffering does. The complete end of suffering happens only when the six senses completely cease, which is when the enlightened being dies. Hence @Akuppa’s question.
So you are interpreting the statement “you will not be here or hereafter or in between the two” as meaning there is no “you” even if there is a “here”. (Ud1.10)
That’s one way to interpret it, and perhaps that’s also meant. However, the “in between the two” quite clearly refers to the in-between of lives. (That’s what it refers to other suttas.) And the in-between is not something most people will have trouble with identifying as a “you”.
So I think the statement can be taken more literally. It means that after the enlightened being dies there will be no “here, hereafter, or in between” as well, on top of there being no “you”, in a sense.