Fair enough.
Now that I think about it, I have noticed the diagonal mixing before. Maybe they were trying to kill several birds with one stone, but the diagonal instrument placements of key instruments sure makes the whole mix more smeared (kinda out of phase-y) to me.
I wonder if maybe somebody at Sony is listening to these mixes and thinking the same thing as me, i.e. this can’t correct?
I think that's probably exactly what happened, because that's what I used to think too - in fact I authored a pretty long
post in the O'Jays
Ship Ahoy poll thread where I laid out the reasons I thought the diagonally panned instruments were wrong, but it turns out I was the one who was wrong.
Some years after that I spoke to Arthur Stoppe, who assisted Don Young on this quad mix (and who mixed many of the other PIR quads) and laid out the same case, and he explained that no, the diagonal spreads were intentional and for SQ compatibility as I laid out in my previous post.
He also said that they never mixed anything in stereo along the side walls (ie left front and left rear, or right front and right rear) because you couldn't hear anything in stereo unless you turned 90 degrees in your seat to face one of those walls, ie turn 90 degrees counter-clockwise and your left ear is pointed at the left rear speaker and your right ear is pointed at the left front speaker, and I think that belief was almost universal amongst all mixers as you'd be hard pressed to find a quad mix that has a stereo element along one of the side walls.
SQ was an imperfect system (to say the very least) and the diagonal "phantom quad center" placements were an imperfect solution to one of its problems, but at least for me, once you understand the thinking, they make more sense in the listening. If these diagonal pans were confined to one engineer, or one studio, you might be able to conclude it was an accident or a mistake, but almost every engineer who did any number of quad mixes used this diagonal method at one point or another. Garfunkel's
Breakaway (and if I'm remembering correctly, Paul Simon's
Still Crazy After All These Years) makes use of pans on both diagonal axes simultaneously in the majority of songs on the album, and it was done by legendary mixer Bill Schnee so it wasn't just CBS's in-house guys doing this stuff.
I'm sure these Apple engineers just get shipped a bunch of .wav files (or similar) and are left to their own devices to make sense of how the channels should be assigned. I dunno if this is still the case, but when the quad mixes started showing up on Tidal, half of them had the channel assignments so grossly mis-assigned that if you listened to them in stereo, the front speakers were in your left ear and the rear speakers were in your right ear. Apple Music seems to be better, but I'd always trust AF & D-V, who both had/have access to master tape boxes and other associated paperwork.
just stunning..!!! 
