Found a possible bug on Warwick's Ultimate

Found a strange interaction between Katarina's E and Warwick's ultimate. Right as Katarina cast Shunpo, I cast Infinite Duress and a few odd things occurred:

 .) The ultimate was interrupted on impact.
 .) The minimum range for a miss did not occur, though I didn't expect it to since it was a pretty spot-on (and good ;)) ultimate.
 .) Katarina's Shunpo was not interrupted, allowing her to follow through and escape un-shredded.
 .) The ability went on cooldown and used the mana required, and refunded neither.

Idk, it could be an intended interaction, but it feels like something that could also have flown under the radar on launch. Feel free to let me know what you think, I'd love closure on the Kat who got away :'(