actually it was mentioned in the comic(asiapic) adaption of roch when dragon girl was using maiden purity(jade maiden)swordplay he speed increased by twice. when you fight usally you use one hand as your master hand and the as secondary. e.g. you throw a right punch then you block with your left.you attack ,then defend. with the left/right technique you can attack and block at the same time. two moves at once .[ in the story zhou butong gives dragon girl a test to see if she can draw a circle with her left hand and a square with her right hand.first she couldn't but then she remembered her emotionless training from the acient tomb. then she could do it.zhou butong was happy and thought her. he mentioned gou jing taught haung rong but she couldn't grasp the essence of the l/r technique.this is because l/r technique is based on bi-concentration but clever people think of many things at once,so clever people can't master this.only people who think straight forwardly and have great concentration can preform l/r technique. ] no matter what skill you practise even if it's kunlun dual sword you execute one move at atime(kunlun uses one technique to use two swords refer hsds). only with l/r it's two different techniques at once to double your speed.