Yeah I think the topic of Ancients and space is weird too. Like, we have Venat coming up with the star trekking bunnies and her Moon being a literal functional spaceship. Given that they're her creations, can we infer that they're based off her own knowledge of how space travel works (and I assume she wouldn't be the only one with that knowledge – much like the Hermes-Dynamis point, I can hardly believe an entire civilisation of immortal academics wouldn't share scientific knowledge with each other, which is one of the reasons why "Hermes had to become Fandaniel!" just bothers me)? Or did she create them with the intent "hey, research space travel for me then build an ark for humanity", which they then did? In either case the end result is the same: logically, space shouldn't be this completely unknown thing for Ancients. But I guess they just willingly chose not to research it much?...
Speaking of, I had long headcanoned (oh
no not another headcanon in this thread!) that the Seat of Nabriales had to do with astrophysics, what with his timey-wimey shenanigans and meteor rain. But Endwalker absolutely did not help out there.