Originally Posted by Seho
Astarion and SH probably really like Halsin, that's why they shouldn't have any problems with it, that's how I read the reasoning.
Absolutely nobody that you don't actively romance likes him, including Shadowheart and Astarion.

If you romance only Halsin, as I said, you should then be allowed to ask the other companions to join in, if he wants only poly and you accept that. It'd actually make MORE sense for Lae'zel and Astarion to tag along in that case, since neither of them will have emotionally opened up to you if you don't romance them. Lae'zel was, after all, open for casual sex in act 1, so if you didn't indulge then, she might still be up for it, and Astarion was doing so in act 1 for protection; now he can get both you and Halsin to protect him.

But again, they didn't do any of this. It just ends there. Because again, he's not actually a poly romance option at all. Just a meme one.