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.
I was going to argue that that was a slightly reductive statement because of all the other groups that the Nazis genocided, but I looked it up and you are correct.