I thought there was a chance this would happen between Gaider's comments and I think one some other dev made a while back on the same topic. Still surprised that they actually went this route though.
I think a previous post that was pretty on point about the decision is that yes, people will be disappointed by this no matter what happens. Of course, a big point that's seemed to come from Bioware on this is making the characters their own character rather than just being available for player satisfaction. They've also repeatedly commented on how they want to make sure that it's balanced and fair which is why I'm fairly confident that people interested in same-sex LI's won't get the shaft like in previous Bioware games (at least as far as this game is concerned). Still, we won't know how well done or awful it is until the game comes out unless you're simply wanting all love interests to be available to your character which now simply isn't going to happen.
About the 'realism' wording, I personally think my previous paragraph saying how its more about making the characters their own people with defined distinctions and tastes is maybe more what was on the mind of the devs when making this decision (any dev feel free to point me wrong). He seemed to know the weirdness or effect the word would have since he stuttered with it, but couldn't really think of any other short way or one-word description for it.
On the realism side though, I do agree with the statements though on how I wonder if this affects race as well since it does seem strange to limit it at sexualities, but not races. Physical attraction's impossible to tell with a character creator unless you specifically had a bar for it like in some old RPGs.
If you truly hate the decision, you can certainly voice your opinions about it, but this is unlikely to change now since Bioware's specifically decided to do this. You may point out the outcry about races, but that always seemed more of a 'We'd like to do this, but we need more resources' case where as this is a case they specifically decided to give the companions/npcs set sexualities. At the moment, the time when they're most likely going to be thinking about changing this in future games is after release where they'll be gathering feedback on Dragon Age: Inquisition's implementation of romances.