Hummm. So it sounds like if the vent doesn’t function at all it’s ok?
There's still a main vent inside the air cleaner that sticks up by the accelerator pump nozzle. The external bowl vent is supposed to keep the fuel vapors from going up the tube when the engine is off and laying in the intake manifold, leading to a richer (tougher) hot start. Considering there are two other carbs doing the same thing (and contributing to idle) without a bowl vent, I'm not sure why secondary venting the center carb matters so much.