I'm not entirely clear on what your question is, but reused single-use propane canisters are lesser for three reasons.
1. The propane they are manufactured with is carefully dried, but propane out of bulk tanks is not. The single use tanks have thinner walls with less corrosion protection because the high-end propane doesn't need it.
2. The safety over-pressure valve on those tanks has similar design constraints and may corrode shut with un-dried propane. Sometimes people damage those valves while refilling.
3. It's easy to overfill those little tanks such that high temperatures can cause over-pressure problems. Due to (1) and (2) the built-in safety measures for refillable tanks cannot be assumed.
I was questioning the idea that having a refilled tank in your car is more dangerous than skydiving. I think it is fair to presume it has some non-zero risk.
I was questioning if that risk is meaningful, or if it is like a prop 65 warning on every building you enter, and most products you purchase.
Googling around I was able to find 1 death associated with refilling a DOT-39 container [1], which is scary shit. However, it seems to be caused by a poor coupling, refilling inside, with an ignition source. This could have happened with any container including a certified refillable one.
1. The propane they are manufactured with is carefully dried, but propane out of bulk tanks is not. The single use tanks have thinner walls with less corrosion protection because the high-end propane doesn't need it.
2. The safety over-pressure valve on those tanks has similar design constraints and may corrode shut with un-dried propane. Sometimes people damage those valves while refilling.
3. It's easy to overfill those little tanks such that high temperatures can cause over-pressure problems. Due to (1) and (2) the built-in safety measures for refillable tanks cannot be assumed.