The four passages on 知禮 in the Lunyu: 3.15, 3.22, 7.31, 20.3 shed some light on 知—is it knowing how, knowing that, or some combination of them, or perhaps a different kind of knowing?
In 7.31, Confucius himself is challenged. Perhaps here we see an ordering (prioritisation) of li? Confucius is challenged again in 3.15. This is a really interesting case: the person who has observed Confucius asking questions at the Hall presumes that Confucius does so because he lacks knowledge. On this basis, he asks if Confucius actually knows li. Confucius’ response turns the tables on the inquirer. To ask questions (i.e. what he was doing then) is not a sign of not knowing that; it is in fact a manifestation of knowing-how to perform li (it is an act of respect or courtesy by a visitor to the Hall to show interest in its details).
In 3.22, Confucius judges that Guanzhong does not know li — on the basis that he has failed to manifest the appropriate li in court. Hence, Confucius asks the rhetorical question concerning whether Guanzhong did really know li.
So here we’ve got some evidence that knowing how is necessary for zhili in these two conversations. *Perhaps even necessary and sufficient in 3.22? (I’m just not sure about this point, though—and I’d like to hear what others think.).