Ah. You misread. Priority mail falls under the umbrella of first class mail as again “private correspondence.”
pe.usps.com
First class mail over 13oz is automatically called Priority mail (under tips in the link) and up above the link notes “sealed against inspection.”
I can understand your misunderstanding, but a little more research might have been pertinent. It is well known that priority mail (which most packs are) isn’t searchable without probable cause or warrant.
In the interest of harm reduction, we need to be careful when making such sweeping statements and causing uproar and fear when it isn’t necessary or warranted.
Again, it would be a different issue if it was multiple packs as Colonial was back in the day in which we shut the thread at the first sign of something wrong.
Edit: OP emailed modmail to delete his account. I will await one more response if OP would like to comment. If not, his account will be deleted tomorrow per request.