I honestly wouldn't be surprised to learn that this happening at least several times per day at pretty much any > medium airport. I witnessed one myself a few weeks ago. Gentleman in his 50s travelling with a carry-on that is slightly but noticeably too big. When it was his turn to board, they checked the size of the carry-on. It didn't fit into the bag sizer. It was impressive watching man in his 50s throw a tantrum about how his carry-on should be allowed, that the world was unfair, that he had booked a higher fare that would somehow entitle him to bring on the bigger carry-on on board, etc. .

Somehow, he managed to get the carry-on into the sizer but then it got stuck and he struggled get it back out. He was eventually reunited with his carry-on and was allowed to take it into the cabin.

I can only suspect that ground staff had enough of his shenanigans and decided that they aren't paid enough to deal with his BS. BTW, it certainly didn't help that he must've had half a dozen of beers before the flight (which board at 6:30 am).