In his other video of him hitting the bag, he was hitting a banana bag. Looked like a TITLE bag if memory serves, I'd guess 100lbs, maybe.
He trolls over on bodybuilding.com though, so when I saw that he joined here I kind of expected this. He posted one or two threads where I actually believed in him for a minute, but looks like he's back to just trolling.
As for the original point, all the talk about "efficiency" while kicking and such: If we're talking about being efficient - people throw plenty of strikes where they don't particularly mean to do damage, feints and such. But if you're throwing a strike with intent to do damage, then you should maximize that in every possible way. Meaning use your hips for the extra power. Using your hips does not use that much energy that it somehow becomes inefficient.
You have a fairly valid point about how an accomplished oly lifter could generate more power than a professional fighter, IF the oly lifter had optimal technique. But an oly lifter's kick technique isn't going to surpass an accomplished kickboxer's kicking technique, so it doesn't matter. It takes as much time to perfect one's roundhouse kick as it takes to perfect one's c&j or snatch, because a roundhouse kick is as much a motor engram as an oly lift. If you don't belive me, let's compare top tier MMA strikers to powerlifters. If you can ignore skill with superior force generation, then powerlifters who bench 500+ should be laying low every pro mma fighter with straight punches all the time. But instead we see guys like Anderson Silva, who aren't particularly heavily built (almost wirey), but who are laying other pro fighters low with jabs, of all things. That's because Anderson Silva and guys like him have been training their strikes for 20+ years.
I respect oly lifters and fighters who incorporate oly lifts. But seriously, you're being silly as hell. You coming in here and questioning the efficiency of the basics of martial arts because you did one or two bag sessions, is like me coming to an oly lifting forum and questioning its basics on the basis of me doing power cleans once a week.
Stop trying to reinvent the wheel. Just get at it, bust your ass, and have fun with your training.
/wall of text