@Vamathi those theories of yours are quite interesting and entertaining. Oh and about Astarion's age - he's a high elf, they live long lives, average lifespan being 750 years. Now he has gray hair, lore wise it's been mentioned many times that elves eternally stay at an adult stage, until they are close to dying of old age, so it's not uncommon for an elf to retain their natural hair color until they are 600 I guess? 700 maybe? I mention this because Astarion's hair and eyebrows are gray, so at the moment of his death, he must've been quite old. For sure more than 500 years old. As to why he has no wrinkles? It could be an illusion, or elves aging differently could be to blame, although, in FR I haven't seen many references to super ancient wrinkled elves. I'm not an expert on elven D&D lore, but I guess I know slightly more than your average person, since I have a huge obsession with elves in games. If I am given a race choice, I will always go elf. In D&D I'm pretty much split between elves and drow (I wonder why in BG3 drow aren't an elven subrace, I blame Larian's tag system).
Anyway, let's just assume Astarion was 500 when he died, add 200 years he claims to have spent being Cazador's slave boy, that would make him at least 700 yr old, possibly older... But that line about PC's ancestor's learning to crawl is... interesting. I loaded a super early save and I got the same scenario to pop up... as a drow.
I don't think races are at all implemented in this line. I mean, there are a few things that raise my brow... but this one is kinda funny. Oh, that would make him older than Ao, if we are supposed to take this line seriously. LMAO
But in all seriousness, I think that Larian, just like Bioware, assumed people would play human (to later scorn the vault dweller Tav), so in that case it would make sense. Also Astarion's biting scene? Makes 0 sense for elven characters, since they don't sleep, they trance. Good luck sneaking up on an elf in trance to suck their blood... it could be possible, but eeeh. Oh another inconsistency in the lore: from the mods enabling origin characters as mains, you can see that Cazador is an elf (has extra long ears)... with a beard (IMPOSSIBRU). So unless he's some sort of https://forgottenrealms.fandom.com/wiki/Fey%27ri (you might have to copy the link and paste it in your browser, for some reason the name fey'ri causes the link to break), what could explain his proficiency in infernal... but that gives me DOS2 Malady vibes, not gonna lie.
Oh and I did read that infernal to latin to english translation of Cazador's poem a while ago, heck, even my little theory on possible soul transfer is buried deep in the comment section of that reddit post.

Well, I'm not deluded into thinking that Astarion is an honorable paladin in shining armor. I know he's a master manipulator. And true, his voice acting being deliberate crossed my mind, altho, there has to be some seed of truth buried within. I mean, come full release first thing I'm gonna do is see the entire game through romancing Astarion, slaying Cazador (I wonder how that will play out really, if there is going to be a way to get Astarion a sip of his blood or will he remain an overpowered vamp spawn forever or will there be other solutions to his vampirism), gonna deny the tadpole and see if it can't be turned against itself. I am curious what type of ending is there in store for all of us, whatever paths we take. I really hope choices will have consequences.
Also, I wouldn't put much stock in Larian's old PR material, since er, retcons happen, plans change.