Some things about about this video: One is the way he is carrying extra ammo. If I am going to use a shotgun for an extended fight, I want more ammo. I have shell bags for shooting sporting clays/skeet that will carry 50 rounds easily. On the down side they have open top so jumping up and down may dislodge a few and going prone might as well. You have to feel the orientation of the round when you grab them so you stuff it in the right way. From a bag you can grab more than one round and have it in your hand as you close the bolt, then you don’t have to reach for another round.
Just to make the practice better I would use multiple targets or moving targets. Shooting 10 rounds at one spot is going to make you screw up in a fight. We use to practice this drill with clay birds thrown one right after the other. You need at least 4 people and two hand throwers. Two shooters stand near each other in the middle, put one thrower on each side of the shooters. (at safe distances)
Start with full guns: Shoot a bird, then the broken pieces, throw the next bird right away, shoot the next bird and pieces non stop, just keep throwing, shooting and reloading. Makes for a real fun day.
As a side note; left handed shooters have a real advantage in reloading a shotgun because you don’t reach over the receiver to place it into the open chamber.