addendum:
I was reading the first AutiBlog issue - google it and get two issues free, including the first issue on both
Autistic & LGBTQI pride,
and found mention of
Autigender - interesting...
just searched up a definition, more here
https://www.queerundefined.com/search/autigender"autigender
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A term for when a person perceives that their experience of gender is influenced by their autism. For example if something about their gender is influenced by a special interest, a sensory experience, or a disconnect from neurotypical definitions of gender. Not usually used as someone's whole identity but a part of it, though some may use this as their only identifier. Not available for use by allistic (non-autistic) people."
I didn't think about identifying as non-binary until some time after my diagnosis.
I only started painting my nails irregularly too, part of it was seeing someone else's nail colours, and now part of it is the sensory feel of having them painted and glossy.
It seems there are more NBs here on WP than anywhere else I have been, online or offline. In fact I have never met an NB before until I came here. I had never even heard of it.
Perhaps some autistic people just don't like being associated with a gender.