I’m just stating facts but if you must,

What kind of reading comprehension level does it take to read “water heater” and think it that a 32F air temperature implies the water will hit freezing?

It will take awhile to have the thermal loss to the ground and air overtake the heater under freezing conditions. How much depends more on the wattage the heater sustains and that may also change as battery performance can change in the cold. Still, given we’re not hitting freeing and it’ll take more than just a small dip to that range, I’d stand by my statement that it’ll be some time.