From the article:
Ok, so your previous message got me thinking there was an extra 5.1 mix made that never saw the light of day. But it was actually just not created.
No, he was referring to the 2003 5.1 mix. The SDE site has more detail from what appears to be the same interview. Here's a relevant excerpt:
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Now you’ve obviously revisited this album in the past. In 2003 you did a 5.1 mix and a new stereo mix
No, no, no. Hang on. Let’s get that bit straight. The record company made the stereo from the 5.1. I wanted my name taken off it because the stereo that was made from that was so bad. It was never meant to be folded down to stereo.
So it was just a fold down version from the 5.1?
Absolutely. And it’s awful! The 5.1 is not great either, but…
Well tell me a little bit about the 5.1 then, because that would have been the first time anyone was trying to do a surround sound mix with this particular record, so you would have been going back to multi-track tapes, dusting them down, baking them and all that kind of stuff.
Actually, the tapes didn’t have to be baked from that period.
It would have been just over 30 years later at the time you did the 5.1 mix [2003], did you choose to try and fix anything or change anything, or did you keep strictly to the whole EQ and the vibe of the original record?
We kept to the original, and one of the main reasons for that was when I was approached to do it by the label, I said, “Look, there are two ways we can do this. I can either modernise it a bit, change things, or keep it the same as it was”. They said “We’d love to have both, but we can only afford one, so keep it the same as the original”. So that’s what it was. It was the original, just [with elements] put in different places [channels].
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To me, it just sounds like they did a lazy, half-assed 5.1 mix mostly because the label didn't want anything too radical or different sounding.The label then took the tame 5.1 mix from Scott and folded it down to stereo without his involvement, and he basically disowns it.