And the reason biological sex is important to females is a very simple one: because of our phenotypical sex, more often than not (and here we go again, the exceptions prove the rule), due to our genetic and phenotypical sex, we are classed as female, and thus, socialized as female, and all the oppression, abuse, and murder we face is justified on that basis by the oppressive class.
No other class of people suffers that; because there is only one other class of them. Males. The exceptions aren’t the ones who are the oppressive class and they certainly aren’t the oppressed class for reasons of mere birth, either. They might be for others, but not for simply being “women”.
Males, on the other hand, from the day they are born, they are socialized to oppress and to rule over the “other”. On the basis of their biology, their secondary sexual features, that stem from – you guessed it – their sex.