For a long time it was in this weird double bind because the federal government mandated generous health insurance for USPS employees, but did not allocate funds for it, because USPS was supposed to provide its own funds to cover all expenses. It looks like new legislation (PSRA) was finally passed in 2022 to move that burden from USPS and onto the OPM.
Anyway it was just a silly joke about how your postal system is state owned but (sometimes) expected to make a lot of money, rather than run at a loss like a normal public service.