I watched the awards now. Theoretically, they could have nominated all companions, if they go for the bi route. Astarion would have the demi sexuality on top (I don't count his canonical samesex relationships, since he didn't had agenda over his own body in that time) and Halsin the poly stuff (though I don't see him as a well done representation of that).
I don't really have a problem with Shadowheart, though I would have prefered Dame Aylin in this case. The game is generally very queer friendly (my view as a lesbian) and deserves an award.
Shadowheart might have been picked, because she is the most romanced character according to Larians numbers.
