I think it would be hard to stop. Each stamp would have to have some sort of barcode or UV marker to differentiate from a counterfeit. Each letter would then have to pass through some sort of inspection to separate the good from the bad. Lot of time and money to make special stamps then sort.

What about the letters with the bad stamps? Throw them in the garbage? Return to sender with a bill?

Unfortunately, it’s become a cost of doing business, and when you see rates rise, this is one of the reasons.

Only thing you can do is don’t buy these stamps. The USPS does not discount the price of rolled stamps, and if you see them on FB marketplace or similar, report them.