I've seen several BNT's use a lariat to prepare the horse for girth and flank pressure, including CA and Dennis Reis. My understanding of the point is that it's like another level of desensitization, beyond tossing the rope all over the horse. The horse in the video was reacting pretty dramatically, but the video was clearly edited for dramatic effect. It's hard to pass judgment over training ability based on videos like that. All shock value, and no information.
What exactly he was trying to accomplish in the clips where the horse is saddled, though, I have no idea. The thing that concerns me most about the entire display is that he seems to have the horse's head tied down in a few shots - with what I can't quite tell; too much dust and too much movement for my early morning eyes to spot it, lol. IMHO, if the horse is that willing to buck, then "headset" shouldn't be a factor at all, much less to the point that the horse is put in some sort of gadget to fix it.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown