I"ve practiced Aikido and seen and felt what you've described. I can't say what you saw was acting or if it was real, but strong pratitioners of Aikido/Daito-ryu can do what you described. Its all about timing, moving the shoulder, the hand, whatever the object of the attack is just slightly, and the right time to throw the attacker. One thing to note, is that the falls themselves, may of seemed more dramatic (I know in Aikido its better for the uke to roll and land safely rather than stagger back off balance, which often leads to "Oh hes just falling for him")
