A couple of points on his post...
1. As I've discussed before, he demonstrates nicely just one of the relationships that should become obvious to you between your neck and how your teeth touch (aka your occlusion). As you pull your chin backwards and nod you will feel your teeth touch in a different spot then when you crane your neck forward.
2. When you utilize poor posture, it causes excessive tension in your face (from the tension of the tissue under your jaw). And it's none too flattering, as he clearly demonstrates!
Thanks Erson!