Huh - the MAC part is interesting. I'm not aware of a way for ZENworks to do that on its own; device name + MAC would have to come from a manually configured registration setting. (That is unless I'm about to learn something new...)

But yes, all such devices should appear in the ZCC until you go in and deal with them. If I see the Machine+GUID showing up, I look at reconciliation settings and make adjustments, then clean out the old, orphaned records, or tag them as retires so that a) they aren't burning a license and b) I can refer to them later.