I was thinking of Yoda. Specifically his words:

No. Not yet. One thing remains. Vader. You must confront Vader. Then, only then, a Jedi will you be. And confront him you will.

Does every Jedi face some right of passage? Or was that specific to Luke? At least it shows that having advanced Force abilities does not a Jedi make. Among the Jedi, it makes sense that some would take up the "knight" role. Some would certainly dedicate their arts to healing or whatever vocation they might take up. I'm wary of making it too categorical of formalistic. I'm content with there being JEDI and within that Jedi Knights. Beyond that, particular talents need not comprise a different sects. Taking on the "knight" role is an elevation in responsibility that I don't think exists in other possible roles.