I get these from deadlifting. I think I intuitively know what he's saying, but I have small hands (for a man of my height), and my grip is pretty weak so I'm already using the thinner 35lb bar. I do mixed grip, left hand over + right hand under, and gripping it the first way adds a bit of friction as the bar tries to rotate out of my hand.
I don't know, maybe I'll try this next time I deadlift but I feel like it would just weaken my already weak grip.
I forgot to add in my first response to your comment: it's worth learning the hook grip to get that additional "friction" you're looking for. https://www.youtube.com/watch?v=JMA2SqaDgG8
Practice hanging from a pull-up bar for time (i.e. practice hanging from a pull-up bar for longer and longer periods of time, using the grip shown in the video) if you want to build up this type of grip. You can also practice by putting bags of rice or a gallon of milk (or two) into a bag, then holding the handles across your second knuckle for time.
Grip is the main way we interact with the world, so it's worth training it. Also, grip strength is the most reliable predictor we have found for life expectancy. (i.e. higher grip strength means higher life expectancy). It could be correlation/causation fallacy, but I have decided to just assume it's worth training it for all the other benefits that having good grip strength brings.
I don't know, maybe I'll try this next time I deadlift but I feel like it would just weaken my already weak grip.