[GAMEPLAY] Nunu W BUG?

I have a question about the blast range of W's snow ball. It appears that if your W hits an enemy as soon as you cast your W, it will be working like Alistar's Q, which I don't really understand? This stun range is clearly out of my imagination....

Steps

1. Shown in the video, walk Nunu close up to the middle enemy dummy
2. Use W to hit the middle dummy
3. Error of the know up hit box occurred

This may not be a bug, but the hit box is quite OP.