Worrying about a customer NOT having their shipments ready if one arrives 5 minutes prior to the PU close window is a red herring.
If a PU Courier arrives at a customer's location 5 minutes prior to the close time, then the Courier makes DAMN SURE the powerpad has the stop 'opened' prior to the close time (so he/she doesn't get hit with a late PU), then scans every package present and works as previously directed. There isn't a damn thing the customer can do to hold the Courier, since it would be prima facie evidence that THE CUSTOMER hasn't done what they are expected - which is to have their shipments properly packaged, labeled and presented for pickup.
The only time this issue presents itself, is when the Courier arrives within the first 15 to 30 minutes of the PU window opening. This is when the customer can yell and scream and the Courier has to protect their hide. If the customer still doesn't have their act together 5 minutes prior to the PU window closing, no one (not even a FedEx senior manager), will take any action against a Courier who scans what is ready, loads it and continues on with his route and informs the customer that he cannot wait for packages that aren't ready.
If anyone has an experience to the contrary (making a PU in the last 5 minutes of a window and having the customer trying to hold the Courier), put it up here with a brief, non-personally identifiable narrative.