I suspect for all carriers across all airports on the planet...it's purely luck of the draw on the ticket counter agent, their awareness of the rules and their engagement to their company. I work in the bag rooms... There's nothing special and nothing in common about the airports on that list that they would have their own set of rules. Carriers and airports can have as many rules as they want....if you have 1 new employee working the counter then none of the so-called rules about early check-in matter. They're paid to process passengers as quickly as possible, not interrupt the process. I suspect in all cases, they just want to get the bag on the conveyor belt and move on. A few airports on the planet have special cold-storage bag rooms (bags checked in > 4 hours before departure. If you arrive at 6 am for a 10pm, they'll probably just take your bag, and it'll spin on the make-up conveyor n the bag room until it's time for your flight,..If it's a domestic flight, they might just load it onto an earlier flight to your destination just to get rid of it.