"The caveat is once a knife is properly sharpened a ceramic or steel will often restore an edge."
Is this just to knock off the wire?
Biscuits
No, if a wire edge is present, steeling may knock some of it off, but that's not its purpose. More than likely, steeling will just keep moving most of the wire edge from side-to-side as you steel. Steeling helps straighten an edge which will leave it, generaly speaking, sharp again for a short period of use.
A ceramic will sharpen an edge, unless you are using the ceramic rod at too steep an angle, and at a fast pace as chefs are known to do (every watch a chef steel one of his knives? Scary stuff). Using a ceramic rod is no different than using the Spyderco Sharpmaker. The rod is an abrasive and running the edge down it will remove steel... a process we call "sharpening". Once again, though, this is assuming you use the rod correctly. Using it at the incorrect angle, incorrect pressure, and contacting the knife to the rod incorrectly will (or can) chip or otherwise damage the edge.