For those who are curious, the cross-crawl pattern is a basic movement pattern that helps allows for added core stability while moving arms and legs in an alternating pattern. For example, sprinting, punchink, kicking, walking, pitching, swimming, etc. When you develop the anterior and posterior oblique sling, you end up with a much stronger and more stable core and can operate your upper or lower body independent of each other if necessary. For example, if Andrew Luck were paralyzed from the waist-down, he would still be able to complete a deep ball pass with accuracy because his throwing strength isn't dependent on planting and throwing off his back foot. This is why I believe RG3 went to garbage after his knee injury, where they rehabbed his knee more than they stabilized his core when they both should have been done simultaneously.
It is far from voodoo. Any physical therapist, chiropractor, athletic trainer, etc. worth their salt knows all about it. It's based of of the teachings of Dr. Vladimir Janda, et all, continued by Dr. Pavel Kolar. It's the primary doctrine of DNS (dynamic neuromuscular stabilization) and embraced by just about every neuromuscular expert from Dr. Stuart McGill to Gray Cook.