"Grok" in is original use is something more like a deep and complete understanding. Here is Heinlein's explanation from "Stranger in a Strange Land": "Grok means to understand so thoroughly that the observer becomes a part of the observed—to merge, blend, intermarry, lose identity in group experience. It means almost everything that we mean by religion, philosophy, and science—and it means as little to us (because of our Earthling assumptions) as color means to a blind man."

But 'grok' is supposed to mean something more like understand various arbitrary things at a low and intimate level, not at a high level.