Again for account purposes yes they should be, for the amount of money they have to actually have to pay future dues owned to employees is less then the amount other government organizations do. Also the USPS is a government organization they just have a some laws that give them some independance; those same laws gave them the responsibility to care for thier employees seperatly from the government norm; something management failed to plan for until forced to.
For financial years 2007 to 2013 the USPS had a total loss of around $40 billion, if they did not have to pay the money to make sure thier current employees were set for health insurance at retirement it would of been a loss of $8 billion. Except for a few times they have not paid into the future health care fund. The future needs of thier employees does not factor into them not having a profit.
It is a lie, everyone has access to thier earning and the laws governing it; and if interested in the topic could easily read them It got started by USPS management wanting the US public to pick up the responsibities that the USPS said they would cover for thier employees so they could continue business as normal with no care. It is the same reason USPS management is wanting to dump its employees totally into obamacare at retirement and not pay any insurance costs for them.
If the USPS differences under law are to considered to be a standard it is a low one, if you say the standard requirement of governement agencies is an A then the standard required from the USPS is a C. They are not required to care about future needs as much as other governement agencies, they do now have to keep accounting planning to the higher standards but don't have to actually use the knowledge.
This is not USPS delivery this is about making sure employees have the health care they worked for at retirement BTW except for a few places, that I very rarely do business with, I require that all packages I get come through USPS.