They're part of the new gamemode. If you've played TFT before, you get "augments" as the game progresses which are like a selection of power-ups you choose from (hence why Lucian has a Shield around him in the Senna Lucian vs. Yasuo Yone fight). I presume one of them is an ult reset if you get a kill.
Pretty much! Though I believe this particular augment (unless it's changed since I last played it) is just that you can cast your ultimate a second time each match, kill or not