Was it not Bruce Botnick who did the Quad mixes? Wasn't he in charge of the original stereo mixes?
Yes, and yes.
And yes, he also did the modern remixes.
Certainly having the original session engineer perform the surround remixes -- at around the same time -- seems most likely to produce a faithful mix (Roy Halee's Garfunkel remixes are another example).
Unfortunately, as decades pass, thumbs start to itch and knobs get twirled in an urge to fix what ain't broke. I wouldn't object to, for instance, adding back deleted instruments in a separate mix so labeled. But fiddling with something iconic and then issuing it as the sole remix is, I think, wrong.