In my enthusiasm to talk about the LE potential, I made a silly extrapolation and didn't stop to think.
We are all aware of the so-called crop effect, ie when, for example, we use a 100mm full frame focal length lens on, say, a 1.6 crop APS-C body. That is the 100mm full frame lens on the APS-C body has the field of view of an 160mm lens on the full frame body. The lens, however, is still a 100mm focal length lens: on both bodies!
The thing that is changing is the sensor size: full frame vs APS-C.
So, my Mamiya lens, attached to my 5D3 by an adapter to ensure focus is achieved at the sensor plane, is still a 45mm lens, and because I’m not changing sensor size, the Mamiya 45mm on my 5D3 looks like a 45mm focal length on, say, my 24-105mm F/4L.
Another way of looking at things is the Mamiya is acting like a tilt-shift lens with no tilt of shift! That is, I'm not using all the glass that is in the lens.
Mistakes are the portals of discovery.