Seems to be a solid concept to me. Not the way i would do it, certainly not at work. The length of your bar clamps would be a limiting factor, and applying a bit too much clamp pressure could bow the sheet and create more problems than it might solve. Not a technique without its problems, but not some horrible abomination either. Looks like a pretty nice shop he is working in there. I'd agree that good technique and a study hand are sufficient for cutting a sheet the size shown in the video.
So file my response to that subject under "Doesn't seem to do much harm, might do some good for some one."