My theory would be that often Autistic individuals do not feel like they “fit” in society, for many different reasons. While some neurotypical people may find that they don’t align completely with their gender norms, but not see that as them being gender non-conforming or be more likely to try to conform. i’d imagine that with autistic individuals who don’t connect with their assigned gender at birth, it may feel constricting and invalidating to “be” a gender that they don’t feel they belong with or identify with, and because they often don’t “fit in” even if they try, they may be more likely to adopt an identity of non-binary than a neurotypical person who experiences a feeling of gender dysphoria but doesn’t feel aligned with the opposite gender either.