While I agree with what you write, ESL speakers often vary in meaning. The discourse and concept you mentioned is one that is part of learning a language. I do prefer for my diagnosis a person with specific diagnosis instead of diagnosis person, too. But that varies by person. Since the diagnosis is something that is an assigned thing, what is constitutional to me is not quite described by it. Though at the same time I am a queer person more than I am a person with queerness.