Oh my gosh you beat me to it!
That video is amazing. I was going to post something like "when the robot uprising starts, it'll look something like this."
The explanation given is equally parts funny and sobering. The suggested root cause was that the RL counterbanance training set didn't include being tethered, so when the corrections didn't have the expected proprioceptive outcome the motions were extrapolated into what you see there.
Also notice how fast and powerful those motions are. current gen humanoids can do some damage. oof.
Alan