Originally Posted by
Pratt
With a nod to Mstateglfer and livedarklions, our ability to balance depends on vestibular input, both static and dynamic, from the vestibular system in our ears, proprioceptive inputs (a sense of our body's position and movement) and visual inputs. When these three sources fail to agree we may be unsteady, fall, and/or experience nausea.
I think that's why the video doesn't really prove much other than if the bike doesn't "behave" the way you're accustomed to, you'll lose balance because it throws off your proprioception. I have no idea if someone could or couldn't learn with practice how to complete the turn under these conditions.