I have never seen this dialogue anywhere, and Astarion loves to hang out in my shorts feed. Very interesting to see it, actually. People always use the buzz term “Rare dialogue” but this is one of the few that would probably actually fit in that category.
Depends on the order of events the game has lined out for you depending on your interactions and decisions. I’ve gotten it both at the grove and the underdark days later depending on whether you accept or reject his first initial request if he asks before the party and what you have and have not finished yet. It can be the smallest things too , like for me I would always get this dialogue at the camp in act 1 but one time I completely ignored him at the tiefling party, so after that he wouldn’t talk to me for days until we reached the underdark lol. Think he got offended. Other times I’d do things out of order and all the dialogue got moved around , so other dialogues would happen at night first before this one would occur.
I always play Dark Urge and it takes 2 more nights for the story. By the time I get to the grove I've already had 3 long rests, so that I don't lose the story and actions with my companions. When I get to the grove, Astarion has about 25 approval,so he almost always offers me the first night very, very early. I had probably never refused before or received his first offer first at the party. For me there were always only 2 offers before. But interesting to know. 😀
