Even then, it's still a no.
Men who have cosmetic surgery/medication/ a bit of paper with a lie on are still men. Sarah Jane Baker being a good example.
They retain male patterns of offending (including using a object if a penis isn't available or functioning). They retain male physical strength and size, they can assault and intimidate women physically just as easily as any other men.
Their presence excludes some women, whose beliefs or needs don't differentiate between men with surgery/meds/bit of paper and men without.
There would be no practical way to enforce that as a rule, especially since you are not a allowed to ask to see a GRC, a GRC isn't proof of anything other than the ability to get the name changed on your gas bill, and politicians want to make them even easier to get. How would anyone woman in a changing room know if the man coming in has surgery/meds/GRC, or is a predator or a chancer? Or all three?
And most importantly, women say no. No men of any kind in women's spaces. Not if they have surgery, not if they change their name, not if they 'pass', not if really want to and will be sad if they're not allowed. No.