Provide a link to an article on this claim, please. I can find nothing about it with a search. What did immediately come up was that UPS...not USPS...is disposing of packages. I also got AI results saying the UK mail service was disposing of them (but then, being AI, it gave no supporting information, and is probably nonsense.) Additionally, I got presented with the USPS regulations for handling undeliverable international mail. It is held 30 days for pick up, then returned...at the sender's expense. If the sender refuses to pay, THEN it is destroyed. If it has no return address, it is destroyed. I used to work for USPS. That has been the policy for a long time.
However, UPS (not USPS) seems to be destroying stuff, and not in as regulated or organized a fashion. Here's an article on this:
https://www.aol.com/articles/ups-disposing-u-bound-packages-054511954.html Document your claim, please.

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UK press has just reported USPS is dumping about 10% of packages due slight errors on custom forms, regardless of value, etc , as they have so much "IN STORAGE" NO DETAILS OF HOW MUCH THEY TRY TO SORT THINGS FIRST!