(Gameplay) Dunkmaster Darius' hidden taunts not working?

So it came to my understanding that darius has several hidden interactions involving the store and many of the other champions. He also has his standard taunts and jokes, but whenever I use his taunt in the proximity of an enemy champ that I know he has a specialized taunt for, he just says his standard phrase instead, for instance, "Nocturne spooky". I am not sure if this is intentional or a bug, but it bothers me that a feature of his legendary skin isn't working properly. Any help would be very appreciated. :)