The dialogue just feels very standard and flavorless (and almost rushed, when compared to other companion's epilogues) when Astarion is usually quite distinguishable, I think p much anyone could say what he said to a romanced PC (that we all deserve happiness etc. I'm not against him saying something like that but it still felt weird to me?). I saw it more clearly during the epilogue with friend Durge where he's hiding a knife, that's a moment where I thought "yeah that's Astarion alright".
This.
Originally Posted by jinetemoranco
It's also confusing that if you break up with him during the ending he says he will look for the Spawn but unless you've told him "we should go look for the spawn" he doesn't do it. It sounds bugged, even though I don't want it fixed tbh.
Maybe he's doing it to spite Tav, like he's saying "I can do this on my own, I don't need you" and wanting to find his brethren because they were people who could relate to him after the only person who supposedly cared for him decided to leave him in a rather crappy fashion.