DadJoke The petition doesn't say anything about the recording of the 'gender status' of the victim. 
FWIW it would probably be useful to record both the sex and the 'gender' of victims so that correct analysis can be done. And actually, yes, it might well be a good idea to record both for the alleged perpetrator too.
But that probably takes time to implement, extra boxes on forms, extra fields in databases...
What is completely unacceptable for crimes committed by one sex to be recorded as the other because of the conflation of sex and gender. That's the immediate and easily solved problem which the petition aims to address. Maybe it would be better if it had been worded neutrally to also include the possibility of crimes committed by females being recorded as by men but in practice they're probably rare and statistically insignificant.