Executioner's Calling?

I remember a week or so ago, Riot said something about bringing back executioner's calling, but giving it some kind of gated condition for grievous wounds, similar to morellonomicon.

And yet, on s@20, it simply triggers off of physical damage dealt on a passive that's always active.

As someone who enjoys drain mages, I'm really hoping this is a placeholder, because free grievous wounds seems like ridiculous value, as well as getting last whisper on the upgraded item. Some Riot input would be greatly appreciated here.