Looking at the practical aspects, a pimple in the middle of the green essentially divides the green into quadrants, or at least "4 halves" (left, right, front, back) and does it while wasting less space than a deck, ridge, or valley crossing the entire green somehow, which divides it into two parts. (i.e., a 10 foot circle is 315 SF, a 10 ft wide stairstep across the green is 10 x 60 feet, or 600. And, the deck, ridge, or valley crossing divides the green more geometrically while the pimple is more random.