Don’t worry, they’re not really menstruating: they just think and say they are. The fact that it’s totally not true is dismissed as irrelevant.
Back in 2015 a poll found 25% of UK men said they had a “period” once a month; and 58% of their female “partners” believed them (https://leeduigon.com/2015/11/19/bizarre-25-of-male-brits-think-they-have-man-periods/). “Coo, love, I can’t do anything with Charlie when it’s his time o’ month…”
How did this happen? I wonder what the numbers would be if they took the poll again today, three years later. “One in five British men believes himself to be pregnant…” On second thought, don’t ask.