Thanks for this, Vexing. I'm in the very earliest stages of transition - I still present as male most of the time, mainly because my wife and kids are still getting acclimated, and my wife and I haven't "quite" figured out exactly how we're going to move forward, but I am presenting as female in more and more situations, and thinking about going full-time sometime in the next six months. And of course I've never been "ma'am-ed" except when I'm dressed (and it still feels a little weird to hear someone refer to me as "she" or "her").
I suspect most of the ones you're referring to are way younger, but you look pretty young, too, compared to me. Anyway, you're right, there are GG's that look quite manly, and many bio-males that look quite feminine, and the ONLY determining factor of gender really is who you are inside. Nobody can tell that by looking at you. If they could, there'd be a definitive test for GID ("I mean, just LOOK at her! Can't you TELL she's really a woman?"). We all need reminding occasionally that our condition goes way deeper than looks.