Not to take the unpopular position here, but I completely understand them not allowing normal shipment of canisters.

Before I'm shunned and banninated, let me explain. I work in the material handling industry, specifically with conveyor systems, predominantly in the bulk/parcel handling side of things. Having seen what conveyors can do to packages that get snagged or otherwise hung-up near drive components, I'd hate to see something pressurized and flammable thrown into the mix.

If you have a package get snagged on a drive, inches from an energized electric motor, and it happens to contain a fuel canister, there's a pretty decent chance that the canister could get sucked under the drive pulley, ruptured, and boom.
Whether or not that's an outside chance, 1 in a million type of scenario, I can't blame anyone for feeling it's not worth the liability, or property loss risk of a big fire.

Freight shipping/LTL shipments of these things is likely going to consist of full pallets of canisters, that are never going to see a conveyor that could chew them up and light a fire.

Sucks for those out in the sticks that can't get their hands on canisters, but alas, alcohol is available damn near everywhere!