[GAMEPLAY] New Warwick E gives him cc immunity

I play a lot the new Warwick in these days, and play against him too of course, and i notice a little problem with his E ability, Primal Howl. The ability says "Warwick reduces all incoming damage for up to 2.5 seconds, or until Primal Howl is reactivated." but happens a couple of time that this bonus also gives him immunity to crowd control effect, like during the leap of his R Infinity Duress.

For example, during a game with Warwick, in early game, i dived a Wukong with my E activated, he pop his ultimate spell (Cyclone) and i didn't take the knock-up, neither when i loss my E buff and he was still spinning. In the same way, in another game, while i was running away from bottom lane, i was hit by the enemy Thresh E (Flay) with my Primal Howl activated, but i have not been dragged to him and i didn't even been slowed. Today i was playing against a Warwick instead, I was Singed, and happens 3 times that, during his E buff, i could not flip him behind my back with my Fling ability.

My friend told me they got the same problem sometime, Is this an intentional thing, but not written in the ability description or it's actually a Bug?

Thank you for your time!