drDave, What idiot gave you that advice? Don't say his name, but are his initials Clem? Well, that explains it.
Been carrying a canister for decades, as I often camp on long trips. No bad accidents so far. Maybe I'm reckless and just plain lucky. I hardly ever park in the sun. The key is a safety approved metal fuel canister with good seals. Not a pet bottle in a zip-lock bag. That's a bomb! Sorry, IED. If you get a gas smell when opening the sidecase, might want to re-think it. My 250cc Honda is quick & easy to drain a cup of fuel for the camp stove, but NOT the R1200R.
If you feel uncomfortable about a propane canister, I would not take it.
Would be very interested to hear what other bikers do. Inquiring minds want to know.