Hi Erik. Welcome to FM.
You're right about the AOV effect for a 645 lens on a full frame vs. crop factor DSLR. I'll use the M645 55/2.8 as an example; otherwise, there are too many "35"s in the discussion. Your C55/2.8 on a FF DSLR will have the same AOV as a 35mm format 55mm lens on the same FF DSLR. The C55/2.8 on a 1.5x CF DSLR will have about the same AOV as a 85mm lens on a FF DSLR. OTOH, the C55/2.8 is a wide angle lens on your 645 Pro body, with a horizontal AOV equivalent to a focal length of a 35mm on a FF DSLR. Oops, there's another '35'.
The MFD for your A 120/4 Macro at 1:1 magnification will not change, but the framing will change, as it will have a horizontal AOV of 17 degrees on a FF DSLR (14 on 1.6x CF), as opposed to 26 degrees on your 645 Pro body.
Jim