On a recent flight, they tried to tell me also that I would have to check my carryon.
I was the last group to be called so I had sat and watched as others who had their supposed ONE carry on and ONE personal item had stretched the limits and were actually taking on items larger than they were entitled, some even seemed to have two carry ons and one personal item.
When they told me to check my carry on, I said that #1, it would hold up the flight as I had to remove valueable first and #2, as soon as I saw those that had three items check their third, then I would check mine. Funny, but they somehow found room for my ONE carry on bag.