Im not much a fan of his theory in that video spuds...
He appears to be sitting next to the rifle with the butt in his arm--not in his shoulder, & he hangs his head over from the side.
You want a rifle to be able to recoil straight back exactly the same every time without choking or hindering it, & his position doesnt allow this...
Also, by locking down the rifle with a hand, you're just preventing the rifle doing what it naturally wants to do...
I think the fact his groups improve by wrapping his hand over the scope is indicative of how bad & inconsistant his technique is in the first place...
Hand wrapped over the scope is potentially a good technique for a 100yd shot on a goat when resting on a rock when you've just climbed a mountain & your lungs are burning as if you're breathing acid & your heart is pumping like your on a large hydraulic jack hammer..& for that purpose i think is worth practicing--but not for good group shooting...
If its a good technique condusive to good groups, id imagine all varmint & long range shooters would do it...
Rather concentrate on a soft shoulder & relaxed consistant muscle tension in your 'butt stock'/trigger arm.
Let the rifle recoil straight back--adjust your position until you get this happening consistantly.
Go through a mini meditation routine every shot if ness until you get good consistancy.
A relaxed shoulder is what you need--let that rifle come back--the more you restrict its backward/recoil movement, the more jump in any other direction you'll get.
Random direction recoil is telling you the rifle is not coming straight back & that you've too much shoulder tension-- it's like bouncing a tennis ball off of a rocky surface--could go in any direction.
Just my opinion...

The man who knows everything, doesnt really know everything...he's just stopped learning...