Dj2
You may not notice it with your canister stove but it MUST happen the same with all compressed gas stoves. Its one of the gas laws from chemistry. The torch pulls off a lot of gas quickly so it cools quickly. If you use your canister stove in 40 degree weather you will learn about this. In warm weather the ambient air can keep the canister warm enough if the flame is turned low. Also the cooling function involves time x rate, so short cooking time wouldn't be so dramatic.

The expanding gas carries off the heat in the can. look up "Adiabatic Expansion Cooling "
Jim
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These are my own opinions based on wisdom earned through many wrong decisions. Your mileage may vary.