Maybe so, and maybe its a poorly designed heating system. The system works with both electricity and propane. It will switch from electric to propane in very low temperatures. As for the safety of propane heat, there is no problem in using properly maintained propane heating system. I have been harping about the need for natural gas and propane furnace maintenance for years.
Propane does require some special attention to venting, trapping leaked gas etc.
The codes and manufacturers specifications appear to address these issues quite well. I have no concerns about using propane, and I use it at my cabin for air and water heating. Ken A - I like easy questions. Concrete board is my choice. There are some lighter weight concrete board substitute products on the market which show some promise.