Not sure if this has been mentioned, but I would never dream that a company has the power to hold a shipment in progress.
I would have thought, once it is out the door, UPS has control over it.
my uncle drives for ups he use to drive package trucks now he drives the 18 wheelers anyway he told me UPS doesnt hold packages if they get it at their facility before a certain they bring it out to your house no matter what the delivery day says. I dont know how that policy will affect the iphone shipments but that is what he told me. I know fedex doesnt do that because i have tracked packages from fedex that get to my local fedex center and they will hold it until the date that was promised to you.