I got to spend some time with Ben a few years ago. When ben putts his putterface is looking way to the left of the hole. At impact it is looking directly where he wants the ball to start. It is the wildest thing! Ben says it is just like a swinger. At address the hands are mid-body so the face looks left, but at impact the left wrist is flat and the face is square.
He uses an arm stroke with no shoulder motion. Just a very clever, dynamic stroke.