This sort of behaviour is not confined to PPL’s. I was strapping myself into the rear of a HS748 when the guy behind me asked, in a very loud voice, who the captain was. He then told the FA to inform the captain that he was a nervous passenger and that he didn’t like “things with fans on the front”. It then became clear that he was a BAC111 captain with the same airline.
When the FA asked him to keep his voice down in case he worried the other passengers, he said that they should realise how dangerous propeller driven aeroplanes were.
All through the flight, and especially the landing, he was telling the pilot what to do. I just looked round at him and yawned.