Exactly. This is the problem with this whole thing.
How do you police such a thing. There are many women who even dressed up in a dress and heels, do not look particularly feminine. There are few ways to tell that are not intrusive of personal rights (looking at genitals or blood test). So how does this get policed at millions of restrooms in the country?
I don’t see a way to do it honestly.
Conversely, when I reported severe sexual harassment by a transgender (mentally ill man) in the women’s bathroom at work, the HR department said it was a spat between two women, have a coming to Jesus meeting to work it out.