Would this be an exercise to prevent tori to think in moving his left arm, rather than his entire body? And thus focus on the other arm to move, which then off course through the body moves the left arm without putting strength in said left arm? If so, I understand. if not, please explain further.
At the most basic level, yes. At a more advanced level -- which I can't explain well because I can't do it consistently myself -- the "movement" is primarily internal, and therefore very difficult to actually see.