I think that's BS!
UPS probably has to have a license, but you don't!
I was Haz-Mat shipping certified in the job I retired from for many many years.
And I didn't have to produce my certification to ship anything.
There was no "license", only a re-certification class every three years to review changes in DOT regulations.
I'd suggest you call a UPS hazardous materials specialist at 1-800-554-9964 and have them clarify the shipping requirements for primers.
Unless Homeland Security has a new requirement I'm not aware of, the USP clerk you talked to is full of it.
rcmodel