Hmm, the Mamiya Universal Accessories pamplet I have states the actual "Picture size" using the Polaroid Land Pack Film Holder w/ Polaroid Film Pack series 100 is 2 7/8 x 3 3/4.
I don't know why your source lists 3 1/4 x 3 1/4
Was there an updated/newer Polaroid holder?
In the Mamiya Universal Lenses pamplet that came from butkus.org only has angle of view information with the Polaroid holder for the 127 4.7 lens.
No other lenses have polaroid data.
It doesn't even list the 75mm
This must be an older version of these Lens specs/instructions.