Good on him. Yes there is no excuse to mess around with people's entitled benefits. A similar thing happened to me. I got overpaid because I was on a scholarship stipend that they didn't recognise. Despite my attempts to clarify and make sure I was getting the proper amount after a year they sent me a bill for $6000 -
One guy in the office told me to appeal but that I would get the internal appeal knocked back then, because the woman who worked there always refuses appeals due to her sticking to some policy or other. When that happened, he told me to put my appeal to the next authority who were external and impartial. He said not enough folk do this and end up paying for something that's not their fault. I did what he said and won because I had declared it and the snooty cow who refused my appeal got a hiding into the bargain!