Just to make sure that we mean the same thing:

On the original RB or ProS: The adapter isn't needed and it can't be used since the mount bore is too small. Likewise the shift and the 500 can not be used on these cameras since theese lenses have mounts that are too big to fit the mount bore in the camera body.

On the ProSD: The shift and the 500 can be used. For other lenses, the adapter is recomended, but the lenses will mount without it. Basicly the adapter fills the space between the lens and the enlarged mount bore in the body. I have a ProSD body, and am using a 90/3.8 lens without the adapter, and I haven't noticed any problems so far.