Thanks!

Weight distribution vs. center of gravity.
While weight distribution (ratio of weight on front/rear axle) is important (x5 has something like 48/62, which some say is even better than 50/50), center of gravity may be even a bigger factor to vehicle stability and feel.
Center of gravity is a spot under the vehicle where a fulcrum could be placed and the vehicle will balance.

B-pillar may not be actually a half point between front and rear. Out of boredom, I just opened side photo of X5 and measured the half point to be a little closer to the front, specifically the middle of the driver's door handle.

The numbers will change by several dozen lbs from front to back.