The drill here is being demonstrated on a straight bar. The ball method can be used on rings in the same way to exaggerate the false grip, but doing this drill on a bar will strengthen the false grip and provide great carryover to the rings if you're learning to do a proper muscle-up.

This is also a great drill to use to build your forearm strength.

Related:  The Most Complete Upper-Body Exercise

Related:  5 More Grip & Forearm Exercises