Yep. Carbs work on differences in pressure. The air pressure on the top of the fuel is higher than the pressure (vacuum) below the throttle plates. This will pull fuel into the motor through the idle circuit when running.
The main circuit outlet is in the venturi, so it needs the air bleed to stop the flow. Otherwise, it will siphon all the time after the first flow is started, if the outlet is lower than the fuel level in the bowl.