Technically I do think a man could menstruate. Transplant a uterus into a man. Manipulate hormone levels to build up and then shed the endometrial lining. And by doing so the man would menstruate. But Lord help us if we get to a place where people start doing CRISPR of some sort to change all XY chromosomes to XX chromosomes. Some of the sequelae I've seen of these attempted "sex reassignment" surgeries are terrible. By the way, disagreement with AAMC standards for support of "gender affirming care" and DEI were the primary reasons for me leaving academic medicine.