So you would prefer she comes and pees next to you at a urinal rather than go to an enclosed stall next to your wife or daughter? You would do a quick scan of the jawline and know she's a dude and wouldn't be at taken aback by it?
I'd be taken aback by it but if he's using a urinal I'm pretty sure it would be pretty clear that it's a man.
And actually if you ask and they clarify that they are actually a man, or if they prefer to say "I was born male" it's usually clear from the voice.