The seperation & carrier level controls on a CD-4 demodulator not only affect how much FR signal bleeds into RR and FL into RL, but also the overall volume of each channel. Almost every needledrop I've done from my own collection needed some kind of balance adjustment on the computer, one corner might be 1-2 dB too loud and screw up the phantom imaging.
It's incredibly hard to get the balance dialed in right on the unit itself (at least in my experience, I'm sure someone else who's running CD-4 will chime in and claim otherwise) and the results are never quite perfect - on my setup now the left channels sound almost completely discrete, but the you can hear the front right content playing at like 25% volume in the rear right and it's aggravating.
The whole point of this anecdote is that you can't really make conclusions about the overall balance or seperation in a quad mix from listening to a CD-4 decode. It's definitely more accurate than a matrix decode, but the four-channel image can still sometimes sound unstable or watered-down in comparison to the discrete master (be it from an old 8-track/reel or a newer digital transfer).
With regards to the way the vocals sound in the Paranoid quad mix - I do remember there's one track (I think it was "Hand Of Doom"?) where Ozzy's voice is everywhere but with slightly different delays in each corner, so it sounds like there's four copies of him singing all around you.