Ask a physics teacher. I know it sounds strange. It's got to do with water level and other mysterious forces.
No. Because when the submersible
pump shuts off the water in the system drains back to the tank through the same hose that is connected to the pump.
It's a cheap way to make sure your plants are getting plenty of oxygen. Plug the air pump into the same timer as your submersible pump so it comes on at the same time.