[Gameplay] Xerath E blocked gy Vel'Koz W

Alright, so today I was Vel'Koz in a game against a Xerath, and I somehow blocked his E with the second proc of my W. We were both very confused and ended up being able to duplicate it again; it seemed that the second part of it (where it comes up like a wall) stopped Xerath's E and made the "hit" animation, as opposed to simply just disappearing.

Is this a known issue? I was really intrigued when I saw it happen.