...to my eye, Endo Sensei's movement also reflected that. What I saw there looked like something of an external approximation of what Akuzawa does...
Specifically, see Endo's video at 24 or 25 seconds, where the uke is doing that sort of fish-flopping and actually seems to be exagerrating it, himself.
Compare that to this whole video of Ark. Does that really look the same?