I have no horse in this race- and, in fact, some biases against Halsin. Nevertheless, eh, I don't think it's that big of a deal.
I don't think it's too crazy that they might've chosen who to make available for poly based on popularity, but I also don't think it's *extremely* OOC for them or anything. I feel like they ran into the issue where most of their cast feels very strictly monogamous, but they still wanted to offer the poly option.
I think with Astarion some people worry about the whole thing because of some lines that could've been handled better, and his backstory making people nervous around the topic. That being said, I don't see why someone with a backstory of SA is obligatorily not okay with their partner being poly.
Shadowheart is complicated because on one hand I can see a bunch of girl next door tropes applied to her because of her romance being a slow burn and her being a secretly soft Defrosting Ice Queen, which to most people tends to suggest monogamy (whether that's a correct association or not), while on the other they've implied she's quite sexually open and/or liberated, often enough for me not to consider it out of character that she'd be okay with several partners (note that someone being sexually adventurous doesn't equal with being okay with polygamy- hopefully I'm making sense here. I mean, see Gale, he's one of the freakiest guys and I can never see him as poly).
Also, to be frank: I don't care that much. I don't want poly, so I don't pick it, and I don't see it.
