Some have a bleed hole to delay them a bit. I don't like or use the secondary pull-offs if the primary has the link up to the secondary airflap shaft, which that carb does. The secondary pull-off is not needed, it's only a back-up to the primary one.
I just not comfortable with a vacuum leak, even a tiny one thru a bleed hole, that will allow unfiltered air to enter my engine.
Even if I use the secondary pull-offs, I block the bleed hole with a dab of Marine Tex......Cliff