Some years back FedEx was shipping radioactive materials to my NucMed dept. Once, when a procedure was cancelled and I tried to ship an unopened package back to the radiopharmaceutical company, it kept coming back to my dept with one or more boxes checked as to why FedEx couldn't ship it.
After the second time I called the local FedEx depot. After lengthy runaround, I finally got a super in the dept that handled hazardous stuff. I told him what was happening, that I was well versed on shipping radioactive material, and that there was nothing wrong with the packaging or my paperwork.
Indeed, I told him that since this particular package had never been opened, that if there was an issue with it, I should never have received it via FedEx to begin with.
He sighed and asked me to ship it to the depot with his attention. He said that some employees were so scared of screwing up and shipping something that they shouldn't, that they would mark something/anything wrong, return it to the sender, and hope that when it came back again, someone else got stuck with it.
Makes perfect sense. I'm betting that this is what's happening in most cases above. Scared to ship the wrong thing so they want to know specifics of a package.