The kill bleed doesn’t monitor anything.

It’s a bleed. Close it off and the center carb vacuum provides a quicker opening to the end carbs.

Try to open the end carbs using a Mityvac with the kill bleed open versus closed.

As the end carbs start to open the Venturi effect helps speed up opening the carbs by “masking” the kill bleed leak.
With the kill bleed plugged the carbs open faster everything being equal.