I don't get the "dry" terminology for ES, wouldn't that be a result of the original production rather than the surround mixers choice of what instruments to place in each channel? I don't consider Hotel California a reference disc either, but it is very good, again, I don't get the "dry" adjective to describe the mix, the recording, maybe.
It all depends. When we say a recording or mix is 'dry', it means it doesn't have a lot of effects like reverb or delay on it.
Most engineers do not record effects onto the raw tracks themselves (though that's not to say it's never been done before, cause it has) because then the effects are unalterable. The effects are usually added during the mixing process.
Sometimes during a mix, an engineer would record a track's effects onto a separate track for posterity, but if that didn't happen and the original effects are only present on the stereo mix tape, that means that an engineer remixing a classic album in surround sound would have to recreate the effects for the new surround mix.
In this instance, it seems Elliot Scheiner decided not to try and recreate the original effects (reverbs, delays, etc.) and go for a more direct and dry mix.
Because effects like reverb and delays are used to create a sense of space and depth (which is harder to achieve in stereo than it is in surround) perhaps he thought his surround mix did not need as many effects on it.
Ymmv, but I hope this explanation helps!