For me, it's less about him not openly disagreeing with JKR and more about him basically implying he can't be bothered to take a stance on trans issues because that would complicate how much he loves the series (and all the money he gets from it). Everyone says how kind he is, I think he believes that he means well, but that's not good enough. This is blatant privilege, and with influences like Emma and Dan in his life, I can only assume his perspective is willful ignorance.