Wasn't suggesting refilling propane, just that you can connect and use a propane 1 lb with a camp stove, using the appropriate adapter (during the canister shortage, I used this option and it works well).
BV not sure of the actual properties of mixing hydrocarbon liquids, but most of the "butane" (i.e. MSR) canisters also contain propane, just for that reason, it extends the usable temp range, as the propane will continue to boil off at lower temps. This will upset the component ratios and eventually during extended cold weather use of gas burning, eventually you get very little output even though the tank still has liquid. That would be the butane component that can't boil off at lower temps.
Since I camp in lower temps as well, I have a dual mode burner which allows me to invert the canister and burn the liquid fuel which gets around the temp limitations usually associated with mixed gas canisters.