OK, let's reframe the question: is somebody who refuses to respect another's personal decision about their gender an HP? And the answer to that, for me, is yes.
There are going to be some exceptions here.
I guess the obvious point would be that no one fully understands Trans issues. Even someone who is trans wouldn't automatically understand the point of view of another who is trans from their background, let alone from a different part of the world, with different social norms and understandings.
Well, yes, but then nobody understands anything.
We should acknowledge ambiguities. That can be especially significant in Trans issues, especially with the debates about letting people who aren't legal adults make major medical decisions. That necessitates an understanding of what we don't know.