Yasuo Wind Wall vs. Vel'Koz

So, Yasuo's wall can block Vel's Q, which is reasonable, it is clearly a projectile. What I don't understand is why it blocks his E, which functions similarly to a Cho'Gath Rupture. It is an instant cast with a delayed damage output, and if placed behind the windwall, it simply never delivers the damage. I can almost see why Vel'Koz's W is blocked, since it starts at one point and extends to another, effectively giving it movement. But it's a crack in the ground. Not a projectile. Any thoughts on those two abilities being blocked? Generic rants about Yasuo are welcome as well, since those are always fun to read.

Edit: I'm blind and oblivious as all hell and somehow never noticed that Vel'Koz throws out purple crap for his E. And while I understand that because of how the W animation and effect is, it technically counts as one, but really Vel is creating a crack in the ground and thus I maintain that Yasuo blocking it is stupid.