You know, I thought I replied to this, but I clearly must've dreamt that up. :|b

I was thinking it was different because the confusion of Stefan's doppelganger was similar to scenes in early S2 for Stefan, where he couldn't tell if he was talking to his girlfriend (Elena Gilbert) or his girlfriend's doppelganger (Katherine Pierce). If that doesn't work, the canon recurrence could simply be Stefan plotting to injure doppel Xander, as he's similarly plotted to injure / maim / kill doppelgangers in canon.