"[...] but the «flameless heater» shows off American tech skills – just add water to the powder in a plastic bag and it heats up enough to warm the plastic meal

"[...] but the «flameless heater» shows off American tech skills – just add water to the powder in a plastic bag and it heats up enough to warm the plastic meal pouch." Wasn't this kind of tech (that involved heating double-deck cans, by pouring water in the lower deck) used by the German army in the battle fields of WW2?