I'd hate to be around when one of his motors goes tits up as he's turning onto final - before he knows what's happening, he'll be doing a pretty decent impression of a pavement pizza.....
I see it differently. It's about energy management. When you're descending from 10000 feet to the ground in 4 minutes, you're probably not using the engines. So, if one quits, he'll probably take to to the shop which the rest of the plane that he's already gliding down. There comes a certain point in every flight where you can plan the rest of the flight to be accomplished on energy in the plane, not engine power. He found that point (at the end of jump run, I think), and used energy from there - just don't damage the engines....
Is flying like this necessary? Maybe not, but then there is a lot of art around which is not necessary either - 'doesn't mean that we don't appreciate it for it's quality!
The jump club always expressed appreciation that i got the 185 or 206 down from 10500 feet in 0.2 hours ('cause they paid for the plane by the tenth), without abusing the engine to do it. My flying was not that artistic, but I did beat the jumpers down a few times....