I haven't been in this thread in a while and I have to say, my dudes I see a lot of cope going on, on both sides. You can rationalize all you want as to what makes or doesn't make sense but the answer is simple. To be blunt the issue is poor writing (whether you want to accept that or you enjoy parts of it) and the writers decision to season his stories with his own sexual interests.
And before someone decides to jump down my throat about attacking the writer or dismissing other peoples feelings, I don't care about your sexual interests and I don't not think less of you because of them. My point isn't to insult but to point out a certain thing. (observation)
He has written three companions (DOS2 and BG3) and in all three companions you can find aspects of cucking. (An apology to the Red Queen, I know you dislike the word but in this case it applies. Unless you can give me another name for it.) I would say he felt rather bold when he was writing Halsin since he also decided to add bestiality, a disgusting fetish that I might add Larian decided to market their game with. (No its not one 'funny scene', Halsin has in game/cut dialogue implying he has sexual relations with animals and the whole drow scene leans heavily into it also. As for those that would defend it by saying he is a druid, would you hold the same position if he were to turn into a child? And the consent thing, lol? Scooby-doo can also consent, at the end of the day you are still having sex with an animal.)
So with that said, no its not a bug, not its not an oversight. Its intended and you are not the audience for his characters. (Maybe these things will change if the backlash is loud enough but the same could've been said for Red Prince and he stayed the same)
As for the whole Mizora scene, yes the poor writing shines the most here since she contradicts everything she has said up to that point. And if you decide to sleep with someone else after the said scene she will go back to her base way of thinking and breaking up with the MC. (Unless its Halsin ofc)
And it was/is used to justify polyamory and the sudden change in character seeing how even the militant poly people of reddit are using that scene as a justification for her being poly. (A lot of people don't care about writing or it making sense but are mainly focusing on their own wish fulfillment with addition of projecting their own lives onto it, that's why you will find poly posters being offended as if you were attacking them.)
If multiple versions of a character are supposed to exist and just closing your eyes/ignoring it is enough then I ask for a scene where Wyll is okay with the MC slaughtering refugees in ACT3 and saying he never cared and enjoys mindless killing. Consistency be damned.
I will say this as a closing part of my post. I don't want to play a side NPC in a RPG whether that comes to the main story or romances. (So I don't want to go through a full campaign where my MC is the main hero only to be swept under the rug in the last 5min because a new NPC showed up and killed the bad guy without my input and I don't want to go through a whole romance where the character decided to cheat and the very end.)
ps. Queen you don't have to worry I probably won't be coming back to this thread any time soon.
I guess I fount cut dialog you were mentioning, still in game yet not triggered:
Lae'zel: You've quite the appetite, Halsin. I'd wager you've bedded more of your foes than you've felled. Halsin: Hmm. A challenging sum. The chimera has three heads... but does it still count as one? Lae'zel: Must have been a challenging kill. Halsin: Kill... yes.