cessation of perception & feeling is dimension, that is false and not even a logical interpretation of the passage.
Cessation of perception and feeling is cessation of all Dimensions or any kind of material or immaterial existence.
This is is because perception and feeling are conjoined, they are same event basicly different interpretation.
https://www.accesstoinsight.org/tipitak ... .than.html
"Feeling, perception, & consciousness, friend: Are these qualities conjoined or disjoined? Is it possible, having separated them one from another, to delineate the difference among them?"
"Feeling, perception, & consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them."
Perception, Feeling, Consciousness these are all Aggregates, they also constitute the Immaterial Realms that can last for very long time but not eternally because there is no system that can eternally provide the conditions for continual arising of a formation material or immaterial, with or without a body.
Actually even an unformed formation would have the potential to gain footing or being formed somewhere if it was to be made somehow, otherwise it is postulating something in the impossible realm again. Ie unborn human would be born in human world.
Conceptual Nibbana, the Knowledge, the "Concept of a thing is not the Thing", in this sense Idea of Nibbana, imagination of Nibbana, Nibbana as we know it, That ceases with the cessation of Nama&Rupa. Nibbana is uncaused therefore not a formation.