Axe/dmg question

Maybe this was brought up some time ago but I was wondering about the way warrior hit a foe with an axe and does dmg. I was watching my warrior last night and i noticed that when he hit a foe with an axe there is a one follow through which goes to left and goes back to original position (right) and hits a foe twice but only when he swing goes to the left actual dmg occur. Can any one clear this up for me or I am missing something.

Animations are just animations; the attack speed is constant.

well animation just animation but the way its setup up that this particular swing hits a foe twice shouldnt be there dmg to this particular swing. and speaking of animation they were probably recorded through a motion capture or designed from scratch but even then its there for a reason to hit a foe but like i said this animation is only trigering dmg command ones and skips when it goes back. and its kind of doesnt make any sence to me.