Press the grip forward to de-loft the putter for topspin
On top of playing the ball about an inch ahead of center, the coach adds a slight forward press, bumping the grip end 'over the top of the ball' to de-loft the putter face. He says the de-lofted face, catching the ball slightly on the up-stroke, imparts topspin and stabilizes the face for a truer roll. Framed as the coach's feel, not a measured fact.
Channel: PorzakGolf
Watch official source at 1:36Why this context matters
Presented as an extra key on top of the one-inch-ahead ball position.