And also developers clearly state in these files that Tav can't get away from him once tadpoles are gone.
It's confirmed. In the script it is also confirmed that:
1. Tav and AA love each other. It says so in plain text. They gaze lovingly at one another and enjoying.
I've recently asked a reddit user the same thing since they were quoting exactly this, but where is this devnote from? I've checked all of the turning night and triggerable kisses devnotes (and other parts of the script that aren't devnotes) and I couldn't find anything like this one.
Regarding this whole Spawn VS Bride debacle, if I may add (more of) my two cents (because I forgot to earlier), the devnotes for Karlach's origin seem to point to the intent being Spawn, as well, since Neil's given instructions to think about how he's soon going to have control of her. Emphasis on the word intent, people are free to interpret however they like. I also agree that if you're sticking with "devnotes are canon" then all of them are, so yes, I will find someone hypocritical if they think Astarion being OK with poly isn't canon.
EDIT: Also, I insist, I feel like it's heavily heavily implied by the flag descriptions for the event at the Elfsong Tavern, so I don't think saying the devnotes never contradict it is true. The wording "Astarion denied the player the ability to break up with him" or "The player can't get away from him, not even if they want to" seems pretty deliberate.
