I have seen United enforce multiple times the policy “2 items maximum” and when they enforce that, they are very strict about it but then boarding is a breeze. It solves a lot more issues than fighting people over the sizer when the real issue is people coming onboard with 3-4 items.

They asked me to put my small cross-body bag in my backpack, i complied and all was good. Passengers with a carry-on, a backpack, a big purse and/or shopping bag, not so happy.

I really wish AC would start by enforcing a similar policy before going down the path they are on.