Tracking USPS Signature Delivery mail- WTF???

My son heard thru the grapevine thru his employer that the USPS has an agreement with Amazon, giving them preference in shipping over the general public.. and if any employee speaks out, their job could come into question.
The post office also delivers for UPS
Also FedEx and DHL.
All are true.
In theory, 1st class, priority and express letter mail has priority over Amazon. Except on Sunday's.
Sundays is to be Amazon only as no mail was delivered on a Sunday anyway.
So, in reality the tracking offered is mainly smoke and mirrors to "let them eat cake"?

BTW what does APC stand for?
I wouldn't call it smoke and mirrors, it's more of a case you actually see more info than you need to. Because you don't understand the logistics of how mail is processed, it seems like your letter/package is going for a tour of the country, when that's not actually the case.
APC is an "all purpose cart". Its this big cage looking thing that you can put thousands of letters in, or a couple hundred small parcels. They have bar codes on them, and when mail is sorted, it's scanned into that APC, the letter or parcel doesn't get touched again afterwards, and all tracking is done off of the APC barcode. When the APC shows up at a plant or processing facility, the APC is emptied into smaller carts.
The APC is reloaded and off it goes to it's next destination. In the meantime, your letter or parcel is still waiting to be processed to a post office and still has the previous APC tracking attached to it.
This is why you see crazy tracking of a letter that tracking shows it goes back and forth or across country then all of a sudden it comes up as out for delivery.
Does stuff go missing? Oh hell yeah! The biggest reason is people don't package things well. If you put a 20lb part into a box, don't pack it well, and when it takes a 40' tumble off of a conveyor, it's going to bust. If not then, it will when the next 20lb box falls on top of it. They process something like 20 million pieces of mail and parcels a day. They loose 100,000 pieces of mail, that's less than .05% of the total mail handled. Seems like a huge number on it's face, but it's actually pretty damn impressive. Doesn't make you feel any better when it's your piece in that 100,000.