IE - you are forgetting one of most important thing for great cornering: low center of gravity.
Regarding 3-diffs in Dynamic xDrive - like I said I unfortunately have no additional info, yet based purely on the press release info I would say there is only one active differential there: on the rear axle. While no active front differential, and no central one.
Maybe I'm wrong though.
It also looks like DPC can be also a stand-alone option - without xDrive. Working like a LSD.