I don’t know enough about it to say definitively, but we still have a rather rudimentary understanding of sexuality and gender that is largely steeped in the binaries of patriarchal culture and I think that is at the root of it.
This definition seems to not reflect the nuances but to resort to binary thinking. “Autogynephilia is defined as a male’s propensity to be sexually aroused by the thought of himself as a female.”
I wish I could give you a better answer but I appreciate the question. This link further discusses the complexities of genetic, chromosomal, hormonal, and cell expressions of sex and gender.