Azir v hec

Just played a one for all game, and my whole team was playing Azir and the other team was playing hec. To my knowledge, I don't play league that much anymore, Azir's ult stops enemies from passing through it, even when the enemy is dashing. Hec's ult is a dash and he can still pass through an Azir wall. I was just wondering if this is a bug or if Riot meant for his ult DASH to be able to go through something that is supposed to prevent dashes. Any information I am missing?