I mean the line IS there and while you don't read it that way the line you just talked about it is also there to support it for people who do read it as implication/foreshadowing similar to the bare skin in the brambles line I brought up a few days ago being readable as an implication of familiarity with casual flings. It's not baseless, it's just not how you read it and it's fine to read it either way. Because either way, the result is determined by player choice in the game.
Then you can also justify Lae'zel being fine with it. She is the fastest one to have sex with you and it's completely casual. Same with Astarion, he'll have casual sex with you quite early.
You two are just blatantly ignoring character development. Something they do in act 1 is no longer relevant if their character is written to have changed in act 2.
What I called baseless is the idea that she's not threatened by Halsin for some reason. NOTHING says that.
