it is a terrible example of throwing a horse into a Mulligan's Stew of loud, sloppy requests with pressure, no meaningful releases and a very confused and ultimately dulled out horse. That horse will soon have NO idea what any feel on that leadline means, and will likely have about the same amount of feel to the reins or bit.
It's not that 'wiggling' the rope to ask for a back is or is not a good method. It's that, one has to remember to ask small, then get bigger, and look for the smallest try you can reward, and build on THAT. Then you build in "feel" to the leadline. Smacking it up against the jaw (and this with a heavy metal chip on it, too) is your "demand", and if you use it over and over, without looking for a correct response, even if it's tiny, to reward and go back to a whisper, you make your horse learn to tolerate incessant shouting. Then, you have an angry and dull horse.