No so the overflow just drains when the return shuts off so it wont have any effect on that switch. It’s more of a just incase for any reason my overflow stockman standpipe becomes somehow clogged and the return keeps pumping water to it. I had a situation last week where it became clogged with algae I was feeding my tangs. ( made changes so this cant happen again but I just want to be sure.) But it caused a rise in my display water level so I also have a float switch on the display itself. This way if either the overflow water level becomes to high, or the display water level becomes to high, the return will shut down until I fix the issue. My sump takes on the extra water so it wont effect either of the float switches.