Why does Edelbrock cut some plenum dividers and not others?

fwiw some ld340 intakes came with the notch and without the notch from the factory.

'I believe' it was the early ones that did not have the notch.

and.....only if the intake is the wrong design/too small plenum etc.. will a spacer help anything.

the notch all the way across is to try and squeeze more r's out of a dual plane, tricking the motor into thinking it has more plenum .jmo