When I was driving truck, we hauled for UPS,FedEx,ConWay, Burlington Air and USPS.
I have been in all of their shipping terminals for more hours than I care to remember.
Believe me, they all kick, throw, slide, shotputt and everthing else to packages. They throw as much as they can into a semi trailer and stack it as high as possible. They don't have/take the time to consider what should go on top of what.
Whenever I had to open the doors before backing in, I always opened and ran, to avoid being covered by the avalanche.