Some POs are more on top of it than others.
AFAIK, they are supposed to scan at acceptance(and mine will do it in front of me if I drop off at the counter and give me a receipt). They then are supposed to get a scan every time they pass through a sorting center-usually an arrival and departure scan.
Unfortunately, sometimes this just doesn't happen.
Here's a "typical" package tracking I might get(from an actual package last week-note tracking is bottom to top)
Cut off is the shipping label date, which was September 20th. That's not exactly unusual for an Ebay seller(or for me)-if an order comes too late to get to the PO for the day, you go ahead and get it packed and ready to go, but don't physically drop off until the next day.
This was another one last week also, though
It took the seller a few days after my purchase to even generate a label, and I'd not be surprised if it took them a few further days to get it to the PO.
Still, though, note that there was no acceptance scan, or any scans along the way for that matter until it arrived at the regional hub. From there it was tracked every step of the way, but nothing from the originating PO until then.