David, you are absolutely right.
I can understand however if a flammable object is to near anything that is heating the same thing can happen. Electric heaters, kerosene heaters, MR Heater propane
heaters, the directions all say make sure you do not operate the heater near anything that can catch fire.
Every year we hear of people that burn down their houses my using a vacuum to clean out a fireplace, they put it away in the closet and it catches the house on fire. The person that puts Gas in a kerosene heater and burns down the house.
It seams that stupidity is the cause of the reason we can not have a gravity furnace
in our campers.