True, although for both of them, I don't know if there was ever acknowledgment of the character's sexuality (which isn't necessary) or if it was up to the player if the companion considered themselves bisexual or PC-sexual. Neither of them explicitly say they have only ever been attracted to the opposite gender before, have they? It can be assumed they have a preference for the opposite gender but not exclusive interest. But yeah, a clearly identifying gay or bi KISA would be better.
Yeah, I see both of them as bisexual, not doing the 'if it's you, it's okay' kind of thing. Though, admittedly, some of the dialogue at the Kaidan romance lock-in on both his and Shepard's part could certainly be taken that way, but I'm already applying copious headcanon to that scene, since I was shouting at the screen 'YES I AM FLIRTING WITH YOU, YOU BACON LOVING IDIOT!' in Huerta when he wanted to 'live in the illusion'... *ahem*
But I don't think of them as the 'if it's you' type, mostly because how I view their characters, it comes from these being characters who aren't prone to making the first move in general, and mechanics conspiring against them - you can't actually flirt with Sky until Dawn Star and Silk Fox's romances are 100% closed out, and male Shepard can't make any direct flirts in ME1. I mean, yeah, you can see a couple of flirtatious lines from them in female runs, but they always seem to skirt the line of able to be interpreted non-flirtatiously. Plus BioWare tends to have a bit of difficulty backing up their words of 'sexuality doesn't matter' in any given setting, so you see these characters unsure of if a same-sex PC is actually interested in them.
Honestly, I think Zevran is a closer example to this kind of character - he explicitly says that if given a preference, he'd go for a woman, though he is attracted to a male Warden. And, honestly, for me, that's kind of a turn off. Not the idea in general, but just the fact that he says to the face of a male Warden 'yeah, I prefer women. Oh, but you're okay!' I don't know, just that handling always bugged me.
In theory, I'm on board with the idea of a fluid-sexuality character, who is having this realization. But I don't really think that I trust BioWare enough to handle it right. I think the better option is just to go with a character who is clearly gay/bi from the start and isn't going to have any kind of identity crisis over their relationship with a same-sex PC.