It's not dependent on developers using it right. They can only make it bad by intentionally messing with the back button. The default behavior, which 99% apps use, is what the parent described. You're already used to this behavior when you press the back button on your web browser.
The developers don't have to use it at all. The overwhelming majority of apps don't touch it.
I know you have to cheer on your team here, but the back button is completely intuitive and users like it; you're creating problems based on what is theoretically possible and not what is reality.
