Darius Ult Bug

Ok I have noticed this bug many times in different games so far including Twisted TreeLine and Summoners Rift, there seems to be an odd bug with ult. His ult is supposed to be IF he gets a kill with his ult that the Ult will still be usable for 20 seconds then it goes on cool down (Rinse and repeat). However while I was playing I noticed that there is another scenario where his ult will auto refresh itself, if you hit a champion with it and they die within a second of casting the ult (Seems to be during the animation when it actually impacts) even if you did not kill them (Meaning the ult was not the killing blow) the ability will still go on its mode to be re-used again.

Its not a huge problem, but its a notable bug that I have seen occur many many times and I decided to post about it.