If you can move in a 2 dimensional plane, such as inside a regular building, you can go in a straight line between any two points.
If you're constricted to moving around the circumference of a circle, you necessarily have to go in a curved line.
Curved lines are longer than straight lines.
So the average distance between any two points is necessarily going to be longer in the Apple building than in a normal building with the same floor area.
Add to that, normal buildings have cores where the utilities are run in the center and radiate out to the edges. Running wiring, plumbing, and ductwork around a circle will involve miles of additional material that would otherwise be unnecessary.
I think maybe you and Apple have a definition of efficient that differs from the rest of the population.