retrofuturist wrote:...it being space is conditional upon the absence of matter.
That's correct in the context of labelling. But there is no other context than labelling when applying terms and terminology like "space". The idea of "unconditioned space" in the context of dharma most likely is evidence for attachment to the idea of an "absolute".
"Space" - besides being used as metaphor - is a term describing mere absence of form. So the context is conceptual mind since the prerequisite is (at least subliminal) memory of form.