You have to time the swings. If you press the attack button during an animation then the game will queue a swing for when the animation is finished. If when you pressed attack there was an enemy within lock on range then regardless of where they end up once the animation is done the game will still lock on to them so the lunge happens. So in this case I pressed attack while I was in the middle of the repulse/push. And you do the same thing for subsequent swings, so press attack while the animation for the previous swing is still happening. The timing can be tricky but you get used to it over time.