I think the rule that dg1 got to flex is "involuntary rerouting." I had this happen to me when I was coming back from LHR in January. They ended up sending me on a direct flight instead of point-to-point without a penalty.

You might try REALLY confusing them and walk up to the EWR counter and check in with the second coupon. I would guess that this is going to require a lot of smiles at an agent for a positive outcome, however.