but you can't see what's inside their mind either.

Not in terms of the narrow scope of "gender identity" where one has this internal, incommunicable sense that they are either a man or a woman, no.

A trans woman who presents as a male won't engender any sexual interest from straight men by simply telling them "I am a woman..." but that's how things are supposedly meant to work, according to TRA's.

I don't mean to be deliberately unkind or unnecessarily cruel, but pointing out the situation as I see it is a kindness, of sorts:

They've jumped into a sociosexual rolling dumpster fire with the transness. Nobody wants to date trans. We have the research. This is the outcome. Somehow I become the problem because I don't want to partner with people who are doing god-knows-what to their bodies with horomones and surgeries. Who have something that is probably best considered a mental disorder with other comorbid psychopathologies. We don't treat schizophrenia by telling people that the voices in their head are real. Why would any reasonable person bother with that? For woke points? I don't care about being woke, and most other people don't care about being woke either. They're just going along with it because they don't want to be accused of bigotry, but they're not really on your side when the bar closes. The hammer on all this stuff is going to fall eventually, and it's gonna be ugly. To me, it's just a question now of who gets dragged down along with it.

This last set of points has an idea irrespective of trans ideology: Why date trans when you have much better options? People try and pick the best romantic and sexual partners available to them. That's human nature. Go ahead, call me a transphobe. I'm not afraid of trans people. I'm simply just not interested when I've got better options.