FWIW, only the airlines can really prevent you from boarding with an oversized bag. If it was one of the maroon coat folks at EWR I just walk past them when they object to my bags. They have no real enforcement power anyways.

A couple weeks ago I was flying to Canada with my wife. I brought our bags to the airport as I was going early and had time. So I had my backpack and two roller bags with me. Needless to say, the maroon coat was not impressed. I simply stated that one was my wife's and that she'd be meeting me at the airport later and walked by. The agent objected but they aren't going to leave their post and there's nothing they can do anyways.