Its never looked right to me either. It looks like when the bowl is full the fuel runs through the center of the pump plunger with a check ball in it.
Even in the 1950's there was concern about fuel volatility (so much worse today).
The hole in the center of the pump, and the check ball are to release air bubbles formed in the pump well by percolation. Without the hole, pressure would gradually build in the pump well, slowing pushing the fuel out of the pump well by way of the pump discharge, leaving only air in the pump well.
Obviously, this condition would mean the accelerator pump would not function on the first couple of pumps until the pump well refilled.
Jon.
