This is purely speculation on my part - but I'd guess that Chrysalis simply couldn't find the original lossless files from 2012 in time for the release, so the quad on the Blu-Ray is a PCM rip of the old DVD DTS 96/24 that was channel-corrected and then encoded back to DTS-HD. If true (again, just speculating here), whatever difference you're hearing might be placebo effect...
Might it be that the original quad on the new Blu-ray is remastered a bit differently? Sometimes a little bit of EQ can be an improvement...or a detriment. Right?