Upside down Left hand grip?

I can’t believe this guy can even hit a ball (and well) with his left hand like this. He claims this grip propelled him from a 50hcp to a +2 in 90 days! That has to be, if true, the largest and fastest improvement ever in golf. I tried a curiosity swing in my backyard and felt like I almost broke my arm.

Thanks for the post.
I always enjoy seeing players leave the mold of convention.

Confirms my own thoughts on not spending too much time worrying about the grip.
Early module work simply puts the hands where they need to be… or at a minimum roughs
them into something workable for each unique student. I may make some refinements later if
necessary, but the pressures and forces felt take care of things for the most part simply because they have to.