This is a "common" problem with BMW, but that doesn't mean it's "normal". Just like many other "common" problems our 7's have that aren't normal.
Anyone who has this issue and thinks it is or was told by dealer it is normal are in denial. A car, especially of this status, should not "jerk" or "move" suddenly forward when turning the car off. That's just ridiulous. If you happen to park close to a wall or a car in front of you then that sudden jerk might just smash your 7's front. Have it looked over by a good Indy or the Sdealer. I remember when my car was having jerking reactions in low gear I was told by Toronto dealer that it was "normal" - what a douche*!