From an FTM pov, I think a lot of you guys are right on the money. The term "full-time" is essentially meaningless for me. It doesn't matter if I wake up in the morning and think, "Alright world, today's the day I present as male!" The world doesn't see me that way. There's essentially nothing I can do for the world to see me that way. It's the flip-side of the "T does all the work" thing. Right now, I'm binding, my hair is short and my clothes are unambiguously masculine. But I've been miss'd and ma'am'd twice now, and I've only been here an hour.
What we regard as masculine is the societal default. Taka is right. When an MTF woman steps outside in skinny jeans and a blouse, she's sending a signal to the world that says "I wish, in some way, to be associated with female-ness." It doesn't matter if she passes or not -- that act, in and of itself, is visible to those around her. Of course, that can be scary, even dangerous. If she doesn't pass, that assertion of femininity can leave her vulnerable to bigots who see her as, at best, a cross-dresser, and at worst, a rapist. The stigma is shameful, and it's not something that most FTMs often face.
I don't wish to suggest transitioning as an FTM is easy, of nor that it's without violence (it clearly isn't; FTMs are particularly vulnerable to corrective rape, especially when in men's spaces), just that it's different, and on a daily basis, imo, less threatening. What it is, however, is a slow grind of powerlessness: invisibility, invalidation, impotence. The fact that many men are clean-shaven is irrelevant because so long as I possess even a whiff of girlhood, I cannot possibly be a man, "real" or otherwise. So why bother to talk about full time? I'm "obviously a girl" despite taking every action to express myself to the contrary. I barely even get pegged as "trans" or gender-nonconforming. My experiences are nothing like that of a trans girl's debut. This is why "passing" gets the brunt of the focus.
There is an element of overlap, though. I wouldn't call myself "full time" by any standard because I am scared sh*tless to pack (ie, to wear a prosthetic penis) most days, because it removes the plausible deniability I might have in the face of anti-trans sentiment (or even just if I run into my neighbor). Realistically, I know ain't no one gonna be staring at my junk, but whoo boy. Makes me nervous.
Does any of this make sense?