I would think you have absolutely nothing to worry about. He did not sound like a psychiatrist so he was telling you it was not his area of specialty. His report will probably say you are under the expert care of doctor x and y and that you are still unfit to return to work. He probably checked that your doctors are real and they are registered. There is no reason to think he did anything else. You explained your treatment and progress. I really hope this did not set you back, it must be so stressful.
This will probably happen again in 1, 2 or 5 years. All the insurance company need is an independent check that you are ill, are being treated and are hopefully on the road to eventual recovery. Whether then you are fit for work or not is a whole other question
social welfare may do something similar from time to time.