Being a PGA Professional and Instructor I can safely say less than 10% of us really know or teach a connected swing.
This is a fact - even many of the highly regarded instructors are smoke an mirrors, snake oil salesman. If you arm swing, set wrists, stay on left side, keep your left arm straight, keep your head down, etc. you will not get good feedback from the harness. I've used this for about a year and it has produced amazing results with my students. The problem with most instructor thoeries involve the arm swing and how it should feel. The Vharness get you to hit with your body, not your arms. If you try to use misguided swing thoeries, it won't work. It gets you to use your body properly and the contact will improve.