[Weightshift]

I don't have a dog in this fight, just making observations. But besides Phil's shot (Phil says that he hits the driver on the downswing and it's very obvious on film), it almost appears (on video)that the clubhead is being "driven down" by the collision with the ball, as opposed to moving down through the ball. In other words, the club looks to be moving down after impact, but not necessarily before.

Do you have a link for a slow motion video of Phil? It may appear the way you describe but if you consider the considerable momentum of the clubface at impact, you know it can't be true. Here's a video of one of his team mates