U ba Khin / Goenka Vipassana putting stress only on vednanupassana

The Vipassana as taught by Gautam Buddha in his Maha Sati Patthana Sutta talks about four different feilds of meditation : Body, Sensations,mind and mental contents. Goenka focuses solely on sensations - Isthis not an incorrect application of Buddhas teaching. If focussing on only one frame of reference could liberate the bhikku, why then would he have specifically mentioned four?