Makes me wonder why some publishers do everything on one disc and others don't. Most of my 3D Blu-rays have a completely separate disc for the 3D version. I think I have only one that has both on the same disc.
I can maybe see if they do some tweaking for the 3D version, like accommodating for the glasses by slightly bumping the gamma on the 3D version, but based on HDD's review, Dredd does this, yet still manages to have both versions on one disc. Maybe just extra compression, since they're fitting two completely different versions of the film on one disc, instead of just plucking one eye for the 2D presentation?
Welcome to Rivendell, Mister Anderson.