I really think you can get hung up on letters. It’s all about if the hearing professional is any good or not. Have they learned from their experience, and do they care enough to apply that knowledge?
I’m closing in on two decades of experience helping people to hear, I’ve fitted over a thousand patients. I could have used that time to earn let’s say four PhDs, if I had the money. Would that make me any better at helping the average hard of hearing individual? Or is my actual practical hands on experience helping people every day to hear worth something? If I were called Master Audiologist Professor Doctor ZCT Esq M.D. does it make me a better person?
As for your question on Audiologists, it all depends on the law of the land. In England I am (was when I lived there and held a current license) allowed to call myself a Hearing Aid Audiologist, even though I have no masters in audiology. Stateside they require an AuD these days, but I believe they grandfathered in the existing audiologists.