Not keen on seeing potential transphobes flock to this like crows to a carcass just because seeing anyone who shares their opinion gets them hard (even if a lot of the stuff they claim can be disproven by a simple Google search + critical thinking skills)
...so I'm going to state my case and leave this thread:
Gender has been a spectrum since before your bloodline even began. The indigenous people where you live have known of it since the beginning. You are but a speck compares to the billions of nonbinary, intersex, GNC (etc) people throughout history.
They are historically documented (and I suggest you actually use Google to search this before making a fool out of yourself next time), but some are not, for the same reason some trans hate crimes are just simply labeled "murders"—if society isn't knowledgeable enough, they just label it as what they know. A "woman who dressed manly" might just be called that, but to his friends he may have identified otherwise.
Anyone on this thread who thinks that identifying as nonbinary because the idea of being a woman/man does not "feel like you" means you are "reinforcing stereotypes" is projecting.
Just because you think all nonbinary people dress androgynous and have societally androgynous interests, does not mean that is the truth. If all nonbinary people dressed as androgynous and refused to like sports or ballet, then I'd agree, but they don't. Your view of the world is limited.
I'd tell you about my nonbinary friends who dress completely binary, but then you'd contradict your own point and say "why do they identify as nonbinary then

"
Nonbinary is an internal identity. Just because you base your idea of being a man or a woman on how society defines them, does not mean nonbinary people view gender that narrowly.
I am a man that dresses and acts extremely femininely, even looking feminine enough that I am called a girl regularly. I am still a man, and my view of my personal manliness includes dressing in skirts and painting my nails.
A nonbinary person could dress the same and have that be their view of
their personal gender identity. Black and white thinking is not conducive to intelligent thought.