I have never heard of such a thing in a conference context, but I have seen it come up in others. And I don't think it's helpful to label such exclusion "hate", as it typically comes from women who feel that self-identifying as female is not sufficient to qualify one to be called a woman.

But it's a very complex and interesting issue, not worth bringing up here, as you note. It's brought up here to stir the pot, I seriously doubt GP actually cares about transpeople at all.

[Edited later: for what it's worth, I regret choosing the word "typically" above. "Sometimes" or "often" would have been more appropriate word choices]