The problem with PCsexual characters is that quite often, their sexuality is left out as a consideration of their past history and experiences (because PCsexuals don't actually have their own sexuality, they merely react to/reflect the PC's sexuality). This is bad writing and/or poor character design, IMHO.
I don't see it that way. I don't think conversations about former lovers is that important in companion's characterization, if at all. How those became so so important that the lack of them automatically warrants them the califications of "bad writing" ? No offense, but this just strike me as the player's need of "proof" for labels they want to stamp on companions. For me, those labels aren't needed, at all.