There is no point in keeping data of anything that is segregated by so-called 'gender', if gender is an optional state.
Aside from crime, figures about pay, poverty, access to education, sexuality (eg has the number of lesbians increased now that straight men can identify as such when they want to continue having sex with women?) and many more categories become pointless, and crucially, there is no way to see where discrimination against women is happening. Are transpeople 'the most marginalised group in society', or could that be women? How can we possibly know, now that we don't exist as a discrete group?
Look what happened at the Brits. At first I thought that was a harmless development (the 'best male' and 'best female' categories were removed last year, and the award became 'gender neutral'). To me, it seemed as though music is not gendered, or sex-based in the way that sport should be, so I was relaxed about the categories merging. But the reason that the women's category was brought in in the first place was that men always won before then, and guess what - it went back to business as before, with no women nominees. We need separate, sex-based categories.
Back to rape - as legally rape requires a penis, there should be no question of it being recorded as a female crime. To do wo would be deeply misogynist.