The worst part for me is that if you go to drow twins and ask them what arrangement they have in mind (sure you can say it should be pretty obvious what they mean, but still) its shadowheart that says: "Thats an idea, if you are comfortable in sharing so am I" If you agree and have Halsin in your party he will ask to join and if you refuse him you get dissaproval message from shadowheart, even if you previously denied Halsin offer of poly. Like wtf is this? Shadowheart is the only female romance option that is slow burn, doesnt lead to sleeping together until act 3, and she is the one that is not only open for orgy, but straight up dissaproves if you refuse? Let's look at her romance for a second: the most you can get from her until act 3 is a kiss. She ask like 3 times through the game if you want to be with her at the end (ending of act 2, act 3 when she talks about future on the farm, and epilogue if you destroy the brain). She straight up says that she never belived she could have real family or real love, which all point out that she is really insecure, and fear/expect abandonment, but then she is the one that acts enthusiastic about orgy? Saying its a good idea, if you are okay with it? (Again, if you just ask drow twins questions she is the one that wants it, you don't need to choose dialogue that is about hiring them)
It's like reverse Lae'zel romance, that starts as casual sex but ends up in her wanting MC only for herself for the rest of life, but you know the difference? There is a build up to Lae'zel attitude change, but there is 0 to shadowheart. If you sleep with any other companion she will end your relation, not wanting to be a spare lover, but suddenly in act 3 she is fine with it? Why? If anything she should be even less okay with it if she abandons Shar that prohibited having lasting relationships. SH/Halsin stuff is more suited for dark path shadowheart but i don't think its even possible then because you won't have a swimming scene (correct me if i'm wrong)
If her dialogue would come up only after you say you want to hire drows, the it would be a different story (but you just need to ask what arrangment you have in mind, I know, its a brothel, so that question might be kinda dumb, but still) . Kinda like Astarion, he act like he is fine with it, but if you listen to narrator he is not, he just put on an act to please you, and it makes MC an asshole for not taking into consideration his past traumas.
Also the epilogue, if she is STILL after everything unsure if you will stay with her in the end, then I don't see how her being not only fine but entusiastic about bringing other people into relation makes any sense
And by the love of Selűne the disapproval message if you reject Halsin in drow scene is disgusting if you want to make sense of it and not just say its bad writing, it's like SH is not fine with being a spare lover but is okay with you being a spare lover for her.