Dear Q.G.
are you really sure about this point that the glass of the 120 mm C-lens (S-Planar) and 120 mm CF-lens (Makro-Planar) is the same? I remember that Kornelius MüllerFleischer from Zeiss said, I think in photo.net, that the 4/120 mm Makro-Planar is recalculated. This is also said in some Hasselblad brochures and in the book off Putkamer, Jeschke,..
When you compare MTF charts, lets say at F8 and image scale 1:5 you can see differences betwen the lenses. You know where to find them.. ;-)
BTW, the time to focus from 8.5 m (closest focus)to infinity with the old C 8,0/500 mm Tele-Tessar is for most people not measured in seconds but in minutes. It comes with a big focusing wheel that serves the same function as the big steering wheel in my old Landrover without power-assisted steering.