To be fair most of the stuff in the transsexual area is blatant fetishization, without anything remotely resembling actual trans women - this discordance might end up being the cause you're noticing: the characters within the category largely don't come across as female - they don't come across as male, either, which implies that they come across as objects.
Or maybe, you simply don't like throwing everything into one bucket and mixing it? Prefer to keep things simple/separate?