Great post, Tong. It took me several years in TGM -- and many weak, 'dying quail' Golf Shots -- to grasp this truth.
Here's one more way to get the idea across. With your Left Hand, pick up a bottle of water, take a sip and then lower it in front of you until your left forearm is parallel to the ground. Take a look at your Left Wrist: It is Vertical. Grip a Golf Club the same way, and you're in business.