Nocturne bug w

After a few games playing Warwick versus a Nocturne, it seems to me that Nocturne's w spell may have a problem...

As it is described, the shield that this spell triggers should act a little as a banshee. Which means that it can block another spell, provided that it is launched BEFORE that other spell. In my case, I launched Warwick's ult, which STARTED (ww jumping on Nocturne, Nocturne being immobilized and, supposedly, suppressed - and hence, muted). But then (and I insist: only AFTER the beginning of ww's ult's animation, say, 0,2 / 0,3 secs later), ww's ult is interrupted (WITHOUT any other player around), and Nocturne got freed and moved away.

Maybe it isn't a bug, as it happened at least half a dozen times per game, but it's strange nonetheless: could that w-spell of nocturne cancel the same way other muting or cc spells after Nocturne has been controlled? it seemed weird to me.