Yep, I think there pretty goofy. If companies have to have an auto fill float I think that's a sign there is some issues, which earth doesn't but a couple do.
With a conventional furnace like earth often times there isn't enough fuel in the firebox to completely boil it dry, at least I know that some companies kind of use that as a safe guard by saying well this firebox will hold x pounds of wood and it holds x number of gallons. So if it overheats there is only enough energy available to boil out 75 gallons of water, or something of that nature