... 'it' refers to which reference?
ref 1 seems to be a series of excerpts of articles
ref 2 is a literature review of historical acounts
neither ref 1 nor 2 is a scientific study, and according to the dates come from around 2000
ref 3 wiki article referencing articles from 2005, ref 4 is science journalism and refers to a 1993 study
remaining refs are all studies from 2006+
So, yes, I didn't know it existed. I've never heard sleep professionals talk about it in my career to 2006ish. Good sleep was pretty universally considered a contiguous segment of uninterrupted sleep with particular cycles by sleep practitioners. My problem is not with the content - I'm open to learning about new things about stuff I 'know' - but with your description of it being something well-known and universally accepted for a long time.
I think it's fascinating, and thank you for providing references. But it's really a very new avenue of formally studied biology.