User blog comment:Shigfugjum/Another Vel'koz Blog/@comment-7945211-20140311035823/@comment-8506165-20140311065642

Wind Wall -actually- blocks everything except the ult. I'm guessing this Yasuo tried Windwalling W after the "projectile" bit was done travelling, ditto the E, and thus it looked like it didn't block them when it would have were it done sooner.

Source: my friend spammed Yasuo for free LP on the day of Vel'Koz's release.