I would assume that's the case because it's commonly used in pornography (see also https://en.wikipedia.org/wiki/Shemale) and males statistically watch more pornography.
The landscape of romance novels might be getting different now, but from what I used to see, a lot of the older romance novels feature mainly standard heterosexual romance. So I'm not sure why there would be a term that's overwhelmingly used as there generally wouldn't be such a term?
I’m not a woman and I don’t consume romance/erotica so no. I’m only aware of how big romance is because I’m a writer, and it’s no secret romance authors far and away make the most money.