It's worse than that. They introduced new stamps with barcodes and let you trade in your old lawfully obtained postage for the new barcoded stuff. They are marking some of their own lawfully obtained stamps as counterfeit and by dint of doing so stealing from their citizenry.
It's roughly analogous to having bought speed guns from an incompetent vendor which sometimes read 200 kph no matter what the speed and insisting their cops continue to use them and ticketing per normal because it would be very expensive to replace the guns.
What, you don’t think the postal court run by the Post Office will rule against the Post Office? Come on, there’s only a small chance of being sent to Rwanda in a crate if you file a case against them, hardly worth worrying about.
It's roughly analogous to having bought speed guns from an incompetent vendor which sometimes read 200 kph no matter what the speed and insisting their cops continue to use them and ticketing per normal because it would be very expensive to replace the guns.