I mean, don't get me wrong. I know some things can look fake. Half of what we learn in hapkido looks fake to those who've never felt it. In fact, when we first started our demonstration team at my dojang, I had to tell them NOT to use half of the hapkido stuff we do, because it looks fake unless you've felt it.
However, when looking at the video, I cannot see anything that would make the person hop back. I see that his push fails to gain traction, which should result in either him losing balance forward, or if he's got a solid stance then he should just be standing there. The only reason I would see to jump back is in the event that the power is reversed (which it didn't seem was the nature of the drill) or if there is some sort of pain compliance (i.e. a bend of the fingers) which I don't see happening.
All I see is that the attacker fails to get a grip on the defender, and then after failing to push him jumps away, seemingly of his own volition.
Now, it's possible that I could experience it and come up with a different understanding. But as it is, I see no reason why that is the reaction for failure.
The reason he jumps is because there is simultaneous redirection which is subtly visible and a push that is practically invisible. Note that the direction of his ‘jumps’ are all slightly off his line.
Being able to manipulate your opponent with little to no outward movement is the hallmark of this branch of Cheng Man Ching tai chi. This is not because it looks impressive for demos (in fact looking fake is detrimental in the long run rather than merely impressive) but because you would have absolutely no visual or tactile cue of any incoming attack.
Again I wouldn’t expect anyone who had not felt this first hand to believe any of it. I have not met Mizner myself so I have no vested interest in promoting him; however I have experienced similar skills from others.
This is getting somewhat off-topic, so I hope my reply gives at least some sort of closure to this tangent.