As I understand JK Rowling, she is saying there should be a word that describes someone whose biological sex is female, and that word should be “woman” - As I understand it, Rowling came across the following term in social media: 'people who menstruate'. She mocked it by responding thus: 'mmhh, there used to be a word for that'. She got a lot of verbal abuse, including death threats, apparently.
A lot of the more extreme debates are just nonsense on both sides - well, not in the recent case of Rowling. She implied that people who menstruate are women, and a bunch of social media activists called her names and made death threats.
How? Most women are not between 15 and 45. Not all women are fertile until 45. Some women are never fertile. I don’t think we need an expert demographer to deduce, from there facts, that most women are not fertile - ok, let me try and reason with you on this.
The majority of women will be fertile for approximately half their adult lives. This means that the average woman will be fertile for approx. half her adult life.
Some women are born without a uterus. Some women are born with a uterus but are infertile. Some women are fertile for longer than the average woman. But all these types of women are atypical because they lie outside the average. None of these groups is a majority.
So, it is intellectually dishonest to try to disentangle female fertility from the word 'woman' because the majority experience fertility in their lives.