I denoted the last part because one could just as easily assume this "someone" was implied to be Spider. Remember that Spider was a result of the copy ability as well, and was in Giga City. Now, maybe Axl thought it might have been Wild Jango, but at the time he didn't know of the Spider impersonation. I mean, in theory, perhaps Spider just so happened to be a real reploid whose name spelled backwards was another Reploid's name "Redips"; And that Redips took the form of Spider after the battle when he took the form of Wild Jango. That, or Redips could somehow make more than one copy while he, the host of the copies, remains elsewhere controlling them from afar, or remain the host within another form, Spider perhaps. Or that he distributed the copy ability to other Reploids working for him, and for some reason decided to conjur up the Wild Jango incident.
But this is all in theory, and unless there's more evidence of this than Spider being the only copy in Giga City, one could assume either situation.