Cho'Gath Ult Indicator [Gameplay]

I've only noticed this for the Prehistoric Cho'Gath skin (seeing as it's the only one I play.) I haven't played him in the last couple of patches, but earlier today I noticed everytime I got someone low enough to ult them either the indicator didn't appear, or it appeared moments later after the target hadn't received any damage. My ult did kill them with or without the indicator however it was a slight inconvenience and I felt it was worth noting,