1954 235 Fuel Pump

[Fred n' Ethel]

Hey folks, I have the flat top fuel pump on my 54 - 235.
The body has the 2 valve chambers separated by a partition.
The cap has matching (smaller) chambers with a matching partition.
The rubber gasket between these is a solid sheet isolating the upper smaller chambers from the lower valve chambers.
Is there a purpose for this isolation ?
Maybe the air trapped in the upper chamber is a buffer ? or snubber of sorts ?
Just curious, thanks for your time.