Originally Posted by Staszek
I think its so they don't have to build two dashboards for Nav and Non-nav cars. (remember the double-hump dash was for nav cars on the existing E90, and the single hump was for no nav)
I think you may be right but more so because of the two screen sizes not non nav vs nav.
From what I read on here and other sites every car gets idrive just like the old E60 5 series, they all had idrive but you had to pay extra for the nav version.