You made some good points, and relating back to the OP's original issues, if the insurer approved his treatment plan, then disallowed it after an audit two years later, it is NOT something that a patient is automatically responsible for. By approving it originally, then even paying for it, the insurer acknowledged it is something they are covering.
It woud appear the current disapproval is an issue between the insurer and provider, and the patient is in no way responsible.
As an example, my chiropractor is having me use his on site gym, calling the sessions physical therapy, even though he had no PT's supervising me at all the whole time I'm excercising. Some years back, my wife had a severe back problem, her chiropractor suggested she take up swimming to build up here back muscles, and she paid a small membership fee at the "Y", and swam several times a week at no cost to her health plan. She paid a for a few sessions with her chiropractor.
I have no beef with my chiropractor, except I find him billing my plan $400 per session using his gym equipment excessive, but I could see he has it broken down to a number of codes on the bills for each session. I told him I'm only going forward because my health insurance is paying for it, and he found it necessary. But I'm not about to shell out $400 to use his gym for an hour's time, unsupervised, if I was paying for it myself.
In the back of my mind, I'm thinking if he get's audited, as he mentioned he might, and my $400/hour gym sessions get bounced, I'm not about to shell out for it, as I already pointed out to him it would be cheaper for me to join a gym, and maybe use a coach. His answer to that was he's got a pre-approval for my treatment, and a coach does not have medical training.
For the moment, I would take him at his word that he is not going to bill me if my insurer disqualifies him. However, based on all the facts and the law, I can't see how he is going to then "bill me" for it later if he changes his mind.

