I wonder if you have considered that a question which, from your point of view, is completely honest and innocent and fair…can actually be triggering to a trans woman?
Someone who 1) has been asked that question 10 million times and 2) understands that your honest question is actually questioning her right to exist in her identity?
A trans woman socialized male does not have the experience of being socialized female.
But a cis woman does not have the experience of being denied her womanhood. You have never been asked to prove your identity as a woman, or outright denied it. Can you imagine what that would feel like?