The government of PA isn’t “ordering” the USPS to do anything. PA is PAYING for the expedited mail service.
So who told the USPS to mail all the ballots out expedited, and charge it to PA taxpayers? Obviously somebody in the government authorized the use of PA’s corporate account number to pay for the postage, and provided the number to the postal service. The USPS didn’t just think that idea up all on theirselves.