How old is he? It sounds like a federal employee approaching retirement and trying to cash out unused medical leave, which you are not supposed to do.
When I started teaching in California, 30+ years ago, it worked like this. You were allowed to accumulate unlimited sick days over your career. If one enjoyed good health, it was possible to “retire” a couple of years early by taking your sick leave. You went to a sympathetic doctor, claimed exhaustion and he would order time off. It was apparently a common-place perk at the time. Yet another reason why Cali has so many pension problems