I think you misunderstand me: Radical Feminism is the belief that patriarchal modes of government are responsible for women’s oppression and must be overthrown through revolution. It doesn’t inherently exclude trans people, but some radical feminists do, leading to them being labelled TERFs, with non-transphobic radical feminists still just being called radical feminists. Regardless of whether you want to count them among feminists, a prerequisite of being a Trans Exclusive Radical Feminist is that you are a Radical Feminist of some form first.
JK Rowling, Graham Lineham, and the vast majority of the GC crowd are not radicals. They do not believe there is anything wrong with our current modes of government. They do not believe in revolution. They are not Radicals Feminists, so can’t be Trans Exclusive Radical Feminists. They are just bog standard transphobes. GC is the term transphobes use to refer to themselves, it’s not limited to TERFs.