That looks very hard to control consistency with…he's basically aiming it manually, and likely varying the amount he takes off, thus the balance, as well as changing the hook angle slightly. I sure wouldn't try it on a well made blade, and the cheap blades (like the one he's sharpening) aren't worth the effort IMO. The cost of the diamond and the cheap blade add up to the cost of a decent blade in the first place. If you've already got the diamond and the cheap blade on hand, can't hurt to try. A sharp cheap blade is better than a dull one, but you've still got the inferior carbide, cheap steel body, and the poor balance to deal with once you're done, so it's not likely to cut like a precision blade even when sharpened.