Charlie held a club out in front of Tiger as he swung though, identical to a drill the legendary instructor Butch Harmon used to do with Tiger, which you can see below.
The goal of this drill is to prevent Tiger’s arms from flinging too far out to the right. When his arms do that, they disconnect too much from his body turn on the way through and can cause the clubface to flip over. So, the only way Tiger can avoid smashing into the club is turning the club more around him.
That’s why, at various other points, you could spot Charlie trying to illustrate the feel of turning his hips more back and through.
Since his injuries, Tiger often struggles with that kind of lower body mobility. when he doesn’t load enough on the backswing, he can’t turn through aggressively enough on the downswing. His arms take over, and his consistency struggles. It’s what makes loading and unloading such a primary focus for Tiger during his swing.
A couple of father-son swing thoughts, to get Tiger going during his final round.