Sergio is an example of the "Malaska Move." The club is shallow out of the top, but never under the plane.
The great dilemma for many players. Do you perfect the swing, or take the swing you have and perfect your game.
Old teaching taught forearm rotation. Modern teaching allows the wrists to release in the way they do for every other sport.
Nicklaus takes 3 hours to hit 30 balls.The greats practice by hitting one shot at a time, and learning from every shot they hit.