The most famous forms of Holocaust denial and revisionism tend to focus on Jews, casting doubt, for example, on how many were exterminated in the camps. But denying the impact the Nazis had on the other groups they targeted, including queer and trans people, disabled people and Romani people, is still Holocaust denial. Maybe someone should tell J.K. Rowling.
The type of Holocaust denial they’re suggesting she’s doing wouldn’t make her antisemitic, because she’s not denying its impact on the Jewish people. It just makes her more transphobic, which we already knew.