“The one who has come to rest, is he then nothing?” said venerable Upasīva,
“or is he actually eternally healthy?
Please explain this to me, O Sage,
for this Teaching has been understood by you.”
“There is no measure of the one who has come to rest, Upasīva,” said the Gracious One,
“there is nothing by which they can speak of him,
when everything has been completely removed,
all the pathways for speech are also completely removed.” Snp5.7
The problem is, Buddha while offering positive epithets to Nibbāna, never describes it beyond the scope of it being peaceful, sanctuary, bliss, and so on; he never went so far ahead to compare it to a function of the mind, he categorically teaches that nibbāna is beyond semantic explanations and categorical descriptions, a significant point you seem to repeatedly ignore.
Peace can not be said to exist, nor can it be said not to exist, and so on, and so forth. It is a category beyond the conceptualization of existence or non-existence, a category beyond categorisation.
The word peace is not the peace. The peace needs no words to describe it, no experience to relay it, no concepts to frame it. You’re attempting to semantise the non-movement, which is not even the word non-movement.
Orthodox Theravāda position is to demonstrate the limitations of language, conceptualisations, forms and to point to a place where these things do not matter. You refer to passages repeatedly trying to conceptualise the unconceptual.
Ultimately, all speech and descriptions of Nibbāna is conventional, because arahants need tools to explain the inexplicable to non-enlightened beings.
Imagine this: I ask an arahant “Venerable Moggallana, are you hungry?” and he replies “Moggallana can’t be discerned, can’t be said to exist, can’t be said to not-exist.” Holy shoes, alright but is there hunger or not?
Likewise, the word nibbāna is not the nibbāna. The word asakhanda is not asakhanda. Yet they’re useful fabrications to help people understand the hard-to-understand, so that the arahant can ultimately drop relying on words, concepts, ideas, experiences, perception, will, feelings, and so on.
This is what we mean by “cessation of everything”, perhaps you should understand it as “cessation of language” because that’s what it is. We refer to a (non-)place where mental formations, our smart analogies, our desperate clingings no longer matter, no longer are useful, just burden and suffering, and everything we could hope to speak is useless and pointless.
Imagine such a peace, that experiencing peace is NOT the Peace.
Silence would explain nibbāna better than words, and even the word silence is not the silence.