A strong core and abs amplify all your existing physical fitness attributes. Developing a strong core however takes time, effort and dedication. The Plank Select workout makes some things easier by helping you maintain the plank position and keep pressure on your core far longer than you would had you just tried to maintain a single position all the time. The net effect is that the need for adaptation felt by the core increases and you will see real physical fitness benefits much faster.
Extra Credit: Keep the plank throughout.