Women also have higher hair follicle density than men to begin with. Men's testosterone makes for larger follicles, coarser hair. So when a woman blasts androgens, they have higher follicle density + male level test = super hairy.
One thing that's interesting to me is that most MTF try to be a caricature of a feminine woman, but fail miserably. Most FTM trans, however, actually COULD be a very convincing man if they just took bodybuilding-style steroids instead of the doctor-recommended dose. Before the IFBB eliminated the women's division of the Olympia, a lot of the chicks would have made convincing dudes if they just cut their hair short and stopped shaving body hair:
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If women take enough steroids and get ripped, they could completely transition without even getting top surgery. (I've competed in powerlifting for over a decade, and though I don't use drugs, I'm around a lot of people who do.) The breasts just go away with that level of steroids and low bodyfat, the voice deepens, and they have to shave their face to keep from growing a beard. I was always curious why more trans women didn't go that route, but I'm guessing it's more because they're actually just butch lesbians, and unlike male troons, their desire to transition isn't based on some obsession with a caricature of the opposite sex's body type.