Anivia Wall - Bug or Feature? You decide

I don't know very much about posting videos or making them or what not, this is an unlisted video but I hope you can see it.

I've played Anivia since season 2 and there are whole months that go by and I play only her. I've noticed this "bug" over the years. This particular one is where you slam them into the terrain with your Anivia wall. My theory is there is a gap between the terrain and the Anivia wall and the knockback effect forces them into the nullspace that exists between temporary terrain overlapping permanent terrain. The counter theory is that there is a bulge big enough to hold the champion model between the permanent terrain and the Anivia wall. This is easy to reproduce and with some practice you can actually predict it in several areas. (The one way gates at the bases as well as any large round convex edge are good spots to get it to work). The outer wall of Summoner's Rift has a lot of little gaps you can trap yourself behind if you are bored and there are a lot of little concave spaces you can use the wall to trap jungle camps and people relatively easily. This isn't what I'm talking about. This is the wall rooting enemies next to terrain that it doesn't make sense to be pinned into.

(Also after watching it a few more times, you can see how effective spellvamp runes are since this is the game I was trying them out for giggles. Looking at it, it looks like I lived cause of the spellvamp runes)