Minion Aggro Question

In the first clip, Dyrus walks behind the enemy's first wave of creeps and is able to fight while only attracting one minion's attention. How does he do this? It's clear that he knew what he was doing from the way he acted, but shouldn't that not be happening? Is it the way he moved, or how he came from the brush directly behind them, is it just a bug? I went through a few of the comments but there weren't any answers so I will allow the NA community to enlighten me.