Wow, that's annoying.

If I see that happening and I'm traveling light enough, I've merged my backpack into my duffle bag so that I have one single "personal item" for under the seat in front of me. Nobody ever seems to care that it doesn't cleanly fit.

But jeez, forcing check-ins during Group 1 is worse than I've ever seen it. I guess it's more and more popular to use two hard-shell carry-ons and put them into the overhead compartment. And I guess the airline just sees it as an incentive for you to buy a more expensive seat.