A disorder also doesn’t really “exist” if it’s not actually causing distress or… well, disorder. Mental disorders are basically cultural constructs in that what is disruptive in one culture isn’t necessarily disruptive in another. “ADHD” in one culture may be “wow, she’s really good at hunting” in another. A schizophrenic person in one culture may be a cleric in another.
Notably, the words the author focused on are all considered offensive now. If a more liberal person were to look for transgender porn, they may not use those terms.