Full time is whatever anyone who thinks the term means anything thinks it means. I have a trans friend who isn't changing her name (it's female enough as far as she's concerned). She could change the marker on her DL (under state law), but she doesn't want to jump through the legal hoops required. That's just not how she goes about things. But I don't think anyone could say she's not full time.
For me, I want to get my DL changed, and it's not a problem to do so. Changing my name is also important, because my legal name is very obviously masculine. It presents a problem.
I consider myself full time, and the legal stuff is just paperwork I haven't gotten around to. But I'm not sure a doctor taking a strict interpretation of the SoC would agree. It doesn't really matter, because the only thing that has any bearing on is my ability to get SRS, and that's out of the question for financial reasons.
So I agree with Natasha, but that might mean different things to different people. For some, it might mean never appearing in public without perfect hair, flawless makeup, manicured nails, and fabulous shoes. To others, it might mean living off the grid in a lesbian artist and organic farming commune in Oregon.