Walking "Under" Naut's Grab?

I dunno if it's a bug or intended.. But last night while playing I managed to walk "Under" A Nautilus Hook several times. He was throwing it from near the red team's blue buff. I was standing in the river near the Dragon. The anchor would fly right through me without hitting me, it happened 2-3 times during the match.

Is this due to the river being at a "lower" elevation than where he was standing, thereby making the hook fly over me? Because that sure is what it looked like.

And if it WAS flying "over" me, and passing me by due to elevation.. Why does that happen with his grab? I've never seen it happen with a blitz or thresh grab, or any other skills in that area.