I think they were referring to 29 actual men who apparently got migrating tumours outside their organs due to taking too much estrogen (for prostate cancer), having liver cirhosis which also fucks with your hormones or being very, very fat, ditto. These tumours form from epithelial cells somewhat similar, in terms of cell type, to the cells lining the edometrium aka the inner lining of a uterus, an organ unique to women. Clue's in the name of course, as endometriosis refers to cells migrating inappropriately from a woman's uterus, not some obscure hormonal problem that affects a tiny, tiny amount of unlucky men, as opposed to millions of actual women.
Of course it wont be long before larping men who have been on wrong sex estrogen for years start claiming to have it and the 29 will mysterioulsy rocket to 2.9 million transwomen have endometriosis as well. I mean, who knows, maybe they will actually a form of endometriosis around their prostates from taking too much estrogen, who knows.