strict. that is how they make their money. bags and carry on normally cost more than base airfare. you won't get a rollerbag onboard but may get a slightly non conforming backpack since when they are busy they don't make every passenger use the sizer at boarding.

they post huge signs at gate and now make anyone who paid for carry on get zone1, that way when it is higher zone #s turn to board they can be on the lookout.

in flying them weekly they shame passengers with any kind of a rollerbag into paying at airport or on app. to the point I have seem passengers passengers turn on the tears at the counter or gate (pretending to not know the policy despite many prompts and warnings on app, website, at checkin, even OTAs).