I have no idea where this notion comes from George. I would always associate “Concordism” with a position involving an historical Adam & Eve, though not all such positions are “Concordist.” For example, YECs typically reject appeals to “two books” theology, b/c in their view they concede far too much validity to the “historical” sciences. Obviously YECs insist on an historical first couple.
As for Concordism itself, I was for many years in that camp. Although I no longer am, I respect it and don’t try to bar the door to it. Here I obviously differ with my very good friend Denis Lamoureux, among others.