Being constrained by external circumstances and factors doesn't make you "less" GNC
I sometimes see some people saying that they'd like to be more masculine (as a woman) or more feminine (as a man), and may even think of themselves as such, questioning if they're "really" GNC because their current presentation doesn't quite match that. Similarly, I've seen some men label themselves androgynous instead of feminine, not because they genuinely want to be more androgynous, but because they fear discrimination and harassment if they were to present more feminine. This is not to say that androgyny is somehow "less GNC" by itself, just that androgyny as compromise or proxy and androgyny for its own sake can be being quite different.
In a society that expects everyone to be either a woman or a man, and every woman to be conventionally feminine and every man to be conventionally masculine, many of us are unsurprisingly constrained by external circumstances and pressures and may find it harder to express our true selves. It's not that I've personally let those constrains deter me from expressing myself more freely, and to some extent, it's not really even practical for me to suppress every aspect of my gender non-conformity (e.g. deeply ingrained mannerisms). However, the very fact that I see the consequences first-hand, almost every day, makes it almost obvious for me as to why someone might make their gender non-conformity less visible, whether as an instinctive response to social pressure and discrimination, strategy, being in earlier stages of exploration, uncertainty, etc.
I do believe that whenever possible, it's best to not suppress yourself within a repressive status quo. At the same time, I don't think everyone's situation is the same, nor that the process of coming out would be identical for everyone. It's ultimately up to you to explore yourself and decide what and how much of it you wish to express to the world.
In any case, I don't think an appearance of "more" conformity means you are "less" non-conforming. You're not "less" GNC simply because you fear assault if you wear "women's clothes" in public. You're not "less" GNC simply because you're a teenage girl and your parents won't buy you that suit nor let you cut your hair short. The very fact that you might want those things, especially if persistently, might mean that your relationship to your gender doesn't quite conform to societies norms... wait... not conforming to gender norms... isn't that just gender non-conforming? Yes.
There's a difference between doing GNC things and being GNC, and so it's possible to be a feminine man who is conscripted into the military and is forced to present more masculine, while still being a feminine man, because that presentation isn't telling you that much about the person, just their circumstances. Ultimately, my point is that while more mainstream discussions of GNC are often about external presentation, it'd mischaracterize many of our experiences to assume that such presentation exists in a vacuum. You shouldn't have to wait for ideal circumstances before being able to recognize your unique relationship to your gender.