Katarina's Ult Reset

Not really sure the technical details of it, But i just had a game where I (as Katarina) did a 5v5 team fight, i watched my ult spin for a good 4 seconds before a cancelled it and chased... and i noticed that it was still on CD... i actually Shunpo'd to a minion and used it vs sion (we both died) just to see if the reset glitched, or the timer itself. So there is currently a situation where Kata can use her ult 2 times, without killing a champion