https://en.wikipedia.org/wiki/Dark_Ages_(historiography)
"The term employs traditional light-versus-darkness imagery to contrast the era's "darkness" (lack of records) with earlier and later periods of "light" (abundance of records).[3]"
Not having records being categorized metaphorically as darkness, and more records as "Enlightenment" is pretty high regard for a word used the same way in the contemporary context as something an accountant or dentist keeps in a filing cabinet.
I'd say these "historians of science" you speak of would corroborate that the lost works of Euclid https://en.wikipedia.org/wiki/Euclid
and the near permanent loss of Plato's works to the whole of Europe for hundreds if not over a thousand years as, uh, kind of a big deal.
https://en.wikipedia.org/wiki/Plato#Textual_sources_and_hist...