I just realized that he's not swinging it like you normally would either. He is taking short chopping strokes, rather than swinging in an arc and letting his front hand slide back. It also does cut at one point when the weight seems to get stuck in the wood. My guess is that you are right. This wouldn't work well for a big job. Also, I didn't mind being shown up by my grandpa a bit. :)
Yeah, if we take a look at the actual wedge: We can see that in addition to the offset angle of the head, it's sort of a modified chisel grind with a lip and a lip going the other way on the flatter side. Not exactly an intuitive shape, but nifty in its own way.
Here you can see what really happens.
http://www.youtube.com/watch?v=E9_9wmjK3j8 Here is comparison.http://youtubedoubler.com/?video1=http%3A%2F%2Fwww.youtube.c... Competition / Speed test http://www.youtube.com/watch?v=lTag8CLWeqw