Many years ago when I did quite a few interviews I wrote relatively detailed explanations to people who had failed to get the job on one occasion. I got two letters. One from someone complaining about me doing this, the other from someone who was pleased to be told the reasons so they could adjust what they did in the future. In the end best probably not to give reasons for rejecting people. Best not to reject people for protected characteristics, but being a PITA is not a protected characteristic.