Just for the heck of it, I thought I'd better throw in my two cents worth...and it might not even be worth that, but here goes anyway.
One of my sons is in UPS Corporate. Here's what he told me. First off, shipping firearms is a big part of their business, probably bigger than most people realize.
Because of that, UPS has standards that far exceed those of Fed-Ex and even the U.S. Postal Service when it comes to shipping hazardous materials, alcohol, and firearms. In addition, they also adhere to the many state and federal restrictions placed upon the shipping of those materials. The reason for the extra caution?? Simple. Like I said, shipping that kind of stuff is big business for them and they don't want to be held liable.
And, yes, if UPS catches some bozo shipping materials in violation of either UPS, state, or federal regulations, the package will be seized. Otherwise, UPS would be held liable.
Hope that helps clear things up a bit.