American fast food is built on one idea.
The same thing, everywhere, always.
A burger in Portland matches a burger in Tampa. That consistency is the product. It is why you can pull off an unfamiliar highway exit at night and know exactly what you are getting.
It is also enormously efficient. One menu means one supply chain, one training program, one advertising campaign and one set of equipment.
Deviating from that is expensive in every direction at once.
So when a Texas chain starts running different menu items in different regions on purpose, the industry reaction is that this is a mistake.
Maybe. Or maybe the assumption was only ever true for a certain kind of food.