I think the generality is mainly true. If I knew zero trans people, would I have thought about my gender identity at all? Probably some, but not much. I tend not to think about things unless they're presented as options (cue me not coming out as bi until I was nearly 30, when I was clued into it by dating a woman).

But also I was pretty gender non-conforming as a kid, and there were times that I didn't want to be a girl. It was less out of gender dysphoria and more out of the way girls were treated back then, though.