I don't think it's so obvious with Sera, but I think that in her case, as well as in case of all bisexual LIs except for Josie, they were written in very "neutral" way, which works just as good for male and female protagonists, besides, for example Merrill actually had different lines for men and women. The plot of Josie's romance isn't gender-neutral, it's based on cultural motive coming from very old times, that is intrinsically heteronormative and patriarchal in its nature. To make it work for a female protagonist it needed serious rewriting.
With the Bi LIs (excluding Merrill), I agree that they were written in a very neutral way, but to me they feel male protagonist oriented. As I said earlier, Sera's romance and interactions didn't feel that way, so I don't agree that one point as far as Sera is concerned. But I think you have some good points about Josie's romance that more accurately explains why I feel the way I do about it. It definitely needs a rewrite to really work well with a female Quizzy.
And speaking of treatment of homosexuality once again, the game states that actually Orlais treats it the best, as "quirk of character", and that it's problem mainly for nobles (because of the need for heirs) and when people are indiscreet about it.
Both of those situations took place in same-sex version of that romance, but no one was bothered by it. They evidently perceived the protagonist, I dunno, as if she was a man.
Yep, that is another part of what makes some of the writing not feel right to me. IDK, maybe it's just me? I like who I am, I'm a girly girl and my partner is a girly girl. I just prefer to be treated as such IRL so I may be a bit biased in that regard.