JMO, but worrying about those sensors is a waste of valuable time. It does not take long to get to know hoow many nights you can go on a tank of water. Measure it in person/nights. My rough calculation is 10gal per person per night.
You will also get to know how many days to need to empty tanks. Those dopey guages can read whatever, you will have a pretty good idea.
Always add a few gallons of water to the black tank to slosh around on the way home or to the next CG. No need to make the tank surgically clean but you don't want stuff drying up in there either.
People get into trouble by hooking up to unlimited CG water without thinking of limited holding tank capacity. The camper drawing from his own freshwater tank is much more concious of his water use.