eubanks the mounting surface on the murray board is actually curved, thats why the center raises up, its curved differently than the rocker and creates a more comfortable stance since the boots are canted in just a tad
Riley is right, it is called a canted footbed and it gives you a more ergonomic stance when riding. Your knees will be in better alingment and could help absorb the impact with your body instead of so much force pushing your knees out.