If you are running a sprinkler controller without a flow meter then it doesn’t matter how you set up the timers it can over or under water. ET calculations just determine how much one should water, not whether or not your system is damaged. To be completely fair does your toilet have a flow meter, because that could run for days as well, and it has nothing to do with the low flow tank.
Not sure what you believe ET calculations do, but it isn’t there to determine whether or not your system is functioning in proper mechanical fashion. That’s like blaming the oven timer for burning your food because the thermostat doesn’t work.
Buy hey thanks for dragging up this thread to blame it for a problem it wasn’t meant to address. You’re more than welcome to spend your time adding a flow meter, just as I have and the system will do its best to manage your water times for you. But at the end of the day you’ll still be responsible for maintenance, and that has nothing to do with “ET world.”
Side note: Flow sensors can be added to all of the controllers that will run the ET firmware. Since hardware version 2.1 current sensing was included and can be used to determine whether or not a valve is functioning. And in both cases the logging functions would reveal the fault, for which a simple script could be used to send a warning email, as it’s unlikely the software could fix mechanical issues.