IDK
Like science is bases on a more rigid and solid based than philosophy and I feel it would be wrong to just start making definitions and such without a base as solid as scienc, what prevents from unintentionally include Shy NTs or left open a gate for those NTs to wish to identify as autistic because spurious reasons?
And if "not needing to use one of the sleeves in my shirt" is a useful criteria to find people with one arm, even if in a "monoarmical" society wouldn't be the case, wouldn't make that much sence to disregard it.
I'm 19 if that works for you, just following wherever people go.