Didn't people already disprove this? Tinder or real-world dating attempts, perhaps not even ugly pictures (a good photographer can make a 6 or 7/10 out of most people). No slurs against women, no fantasies of rape or sex slavery, no "porn rating" for the woman ("nice big tits" or the like). No woman at Tinder or at a speed dating should be able to know about such upfront, if not spoken. Even less about a small dick.
Many incels actually don't look ugly on their pics, but they still can't get anything. Maybe there's some kind of hidden codes or "aura", that turns women away.
For J.K. Rowling: I think one should a bit separate the works of a person from the person itself. Even if somebody is really horrible or has at least some flaws, the novels, movies, songs, video games or whatever can still be great. What J.K. Rowling says is probably just female bluepill, belief (delusion, not lie) that any mediocre man can get a woman. Female redpill behavior is probably more subconscious; they say they might date a mediocre guy, but once they actually come across one, they're quick to get away.