It is a matter of precision,. Were one to break boxing down four factors it would be speed, power, direction and angle. Whitaker was able to perceive the speed of a fighter, his power from a certain position, his exact balance, and the angle between him and his opponent to a much finer degree than any of his opponents. As Pop would put it, he could measure to three decimal places, while his appoints where stuck at one. This more exact information allowed him to go almost his entire career without taking a punch while delivering perfectly places punches himself.
The lesson I suppose is that an incremental improvement in perception allows a categorical change in the quality of the action.