Last week, the dragons at the bottom of the escalator to Pre Check at LAX T4 were in rare form...they were making everyone put their bags in the sizer, even when it was obvious they would fit. A woman in front of me had a compliant duffel bag, but when she put it in the sizer, one of the outside pockets got hung up on the metal rail, so the dragon said she had to go check it. The woman lightly tapped the pocket and the entirety of the bag was then within the confines of the sizer, and she then took the bag and went up the escalator while the dragon yelled after her to come back. LOL
I don't understand the application of the baggage "rules" pre-security. The requirement isn't to have a compliant bag at time of security, it is at time of boarding. And I understand if AA wants to use contractors to help with enforcement, but IMHO this should only be done when there is an AA employee nearby to adjudicate (such as at the gate).