Here is a better idea of how FedEx works from an ex-employee.
Apple will print labels with assigned numbers at their facility, hence received tracking number, which is how their system operates. Phones will be loaded on semi and off-loaded at FedEx facility. At that time, the shipment will be scanned into FedEx and you will then, and only then, begin to see movement.
Just because a number is generated, they could be trucked across country from Apple distribution center to FedEx hub, so updates might not begin until the middle of the night when they hit these large centers.
FedEx has several delivery options, so if Apple wants them all to be delivered on Wed or Thurs (I keep reading different days), they can be held across the country and meet these criteria options.
And yes, FedEx is highly trained on handling these types and numbers of shipments efficiently, so the nice thing to do is NOT to try to bring down there servers which only impacts normal business activities, health needs, etc.
What a dumb idea, I wonder how ctt1wbw would feel if he was on operating table waiting for medical shipment that was held up by selfish IPhone users.