I don't think it matters so much if the therapist/helper is a "Dr." of any kind; it's more about whether they follow a medical model of treatment or not. A "nurse" is going to call me a patient but a social worker is probably going to call me a client, unless the social worker is also a psychoanalyst of the "couch"/Freudian school in which case I might be a patient. It's their conventions/mindset; may or may not align with titles or degrees.

I don't care what anyone calls me as long as it isn't late to dinner ;-)