Well, I guess that's a non-issue for me since I don't plan on being in -30F temperatures. To your point, though, is it any different than not having the CheapHeat and running out of propane, freezing up a regulator, or?? There's no back-up for that situation either insofar as furnace operation is concerned.
I don't use the CheapHeat when our 5th wheel is in storage. Our CheapHeat system is wired for 50A, and our covered storage bay has only 30A service. On the few nights on the Texas Gulf Coast that it might drop below freezing, I use electric heaters backed up by the propane furnace.
The system works fine for us. If it doesn't for your application, that's OK as well.
Rusty