Good point. I shall see very shortly with the development of the first "after crash" film. It is quite obvious that the camera is no longer suitable for critical work anyway, my only concern would be to keep it for casual shooting.
I am still not understanding how the flange to film distance is important here : suppose the flange is pushed inside (and kept perfectly parallel, which we know is not true of course), if the helicoid movement compensates this, the geometry is the same as previously, only the focusing distance indicates, say 3m where in fact we are at infinity, but that would not be a problem if we use the ground glass for focusing (and here I agree with you that we must assume it has not moved). I don't mean to stir pointless contradiction here, I'm just trying to understand where I missed your point.