He uses a grip that favors the right hand. When I putted left hand low this is what I used. The stroke is pushed with the right hand. The left is simply locking it so it doesn’t break down. Instead of how most do which is to pull through with the left.
He interlocks his right index finger with left pinky then puts right middle finger underneath sitting on the back of his left hand.
His trail hand is also very palm up which strikes me as unusual. It actually somewhat hurts to hold the putter in that position. Face feels locked in though !!!