Good question. Clearly hitting the ball from the tee or on the fairway, there is a vibration from impact that the MSB can sense.
The putting is another question as you note. Perhaps it has to do with frequency and motion rate. In other words, most people take couple, three practice swings rather rapidly. Once real shot/stroke is made, players tend to hold the finishing position longer than practice swings. Its that pause period that may distinguish the difference, in addition to vibration feedback. Also, there is a sound associated with hitting the ball, including putting. Microphone could pick up that sound...
Just rationalizing.