I realize this is an old thread but had a related experience today. Flying ATL-PHL on an E175. I have a fairly standard 22" Travelpro rollaboard. At gate, agent tells me it won't fit and that I have to check it. I said I wanted a yellow tag but they forced me to check through to bag claim in PHL

So, I get on the plane, and I see that the overheads are not deep enough to put the bag in wheels out, but it certainly looked like my bag would have fit.

Was the gate agent mistaken? Should I more politely have pushed the issue? It didn't make a lot of sense to me that if the plane did not have overheads large enough to accommodate regulation size carryons, that a "yellow tag" gate check would not be offered.