I think this is a much more nuanced conversation.
On the one hand, of course menstrual leave as standard is a ridiculous concept.
On the other hand, there absolutely are women whose periods are debilitating and for them, some reasonable adjustments can and should be made.
But then, what are those? And how do we make them? with any other disability or illness, there would need to be some kind of proof. You can't just say, "I have migrains so i'll take time off whenever I like". Instead, if it's an ongoing issue, you would need information from a doctor, specific assessment of your specific cneeds, and a solution that works for both you and your employer. It would have to be similar in this case.
But then we come up against the next issue - women's menstrual issues rare routinely not taken seriously, nor are treatments particularly well understood or explored. The poster upthread who talked about 7 day heavy bleeds etc for 40 years being a case in point. This is NOT normal, and yet she's spent her life thinking it is. OP has pointed out that she's tried to seek help but got nowhere. We know, for example, that endemetriosis takes, on average, 10 years to diagnose. 10 Years? That's outrageous. So you could, once you have a confirmed diagnosis, perhaps ask for help... but what do you do for the 10 years before that?
I am self employed in a job that involves quite a lot of concentration and thinking work as I integrate research and analysis into various pieces of content. As peri menopuase started to kick in, I realised that I had about a week a month where I coul dbarely keep up with basic admin. I was lucky - it only took about 18 months for me to get this stabalised. But that's still a ridiculously long time, and that doesn't inculde how lng it took me to even realise the problem in the first place.
So no, menstrual leave isn't and shouldn't be a thing. BUT we absolutely can and should do better for women.