Unfortunately, Siegfried for whom I have a lot of respect, is still very much stuck in the dark ages of stereo reproduction.
He has tried to convince me and others to do more research in the perception of stereo reproduction, as noted in his review of of
Floyd Toole's book:
I quote him" ..My only regret is that the potential of 2-channel playback in doing so has not been fully explored. "
I think it is well-established scientifically that the potential of 2-channel audio is very limited (in terms of spatial envelopment, apparent source width, localization, wide sweet spot, dialog intelligibility, better timbre from discrete sources versus phantom images which cause cross-talk cancellation that shifts with head movement) when compared to multichannel.
Personally, I think such research effort is better focussed on improving multichannel audio recording/reproduction. Stereo is dead. Multichannel is the future. Let's move on.