So no commentary tracks on the one disc... but 3 on the SE. They aren't the same discs then, yes..? Could there be less bitspace for Video on the SE movie disc. I watched the single disc version and the bitrate was quite high, in the 9 region and tapping 10 sometimes...
I think the same applies to commentaries. Three commentaries don't take up that much room, and thus it would be inefficient to re-encode the whole thing just so one consumer can see the difference three inches from his 100'' screen.