This is true... I was a chef in another life (long ago) in a restaurant where we did most of our own butchering and cleaning of produce. Stocks cooked all day, started by the A.M. Sous Chef and finished by the P.M. Sous chef.
Of course we had 100 and 150 gallon steam pressure cookers too that cooked on all sides and bottom (double stainless steel with steam circulation).