I think that being externally trans (I dislike the notion of 'passing' and 'not passing' though, as unfortunately necessary as they are) allows that transparency. I agree with others that by being externally trans, people who are genuine approach you with honesty!
I remember a moment while taking the bus with my boyfriend. I saw a visibly trans sister on the bus in her early 40's at the front, with who I presume was her mother. It actually made me so happy, that I wanted to shout "LOOK I'M TRANS TOO! SISTAHZ! EEEEEEEEE!!" but I knew it would cause a scene.
It any case, she looked content and serene, and I sent her a mental blessing! The rest of us can be comforted knowing that there are trans people in the population!