This clearly isn’t true since plenty of people get access to psychotherapy who have public and private insurance without being diagnosed with a specific illness.
Every time I look at a therapist while seeking treatment, they always put a disclaimer on their insurance page that a diagnosis is required to be paid for claims. Maybe it's just my state.
Will insurance really cover a psychiatrist without a diagnosis? I always assumed the doctor was reporting a diagnosis to the insurance company even if they weren't telling the patient.