This sounds like false advertising to me. The website says U122CX, then that is what you should receive, of course.

As noted, the U122CX is actually too long and will definitely not fit into some overhead bins.

I have the U121CXW-4, which actually meets AC's size requirements, though it is a slight bit too wide for UA, AA or DL. Never had a problem with it, and it fits a ton of stuff.