The elephants in the room.
Okay, 600 but I'll bet there are far more fires caused by faulty wiring. Anyone want to take that bet?
Elephant in the room #1
Yes, IME, faulty wiring is the big problem, but why? Humans.
I'm going to say those stats are human driven. I'll bet that nearly all electrical fires are caused by human error: like shortcutting or simply not reading the instructions; rather than a defect in an electrical part or wear & tear.
IMO, all the big risks in electrical systems can be mitigated fully by simply following ABYC codes, reading the instructions, and asking for help when something isn't understood.
Elephant in the room #2
Propane installs, especially in recreational settings, suffer from the same human problems that electrical systems do but not all the risks can be mitigated.
The saving grace of most propane systems, and I'd suggest the reason there are fewer propane accidents, is that most of the time the supply gets shut off when one is done with the BBQ or stove. Even when there's a little leak in an old or worn system, it stops leaking when the supply is off.
Refrigeration though, requires an 'always on' supply of gas, which means little leaks can be 'always on' too.
Wear and age related leaks in a propane system don't have a 'fuse' to stop little leaks. (There are ways to automatically catch big propane leaks, just not small ones.)