What actually happens is this: Apple works in secret on the next version of macOS. Apple makes changes in the next version of macOS that break an app on the internal list of "do not break" apps. But Apple can't tell the app developer about this, because the changes in the next version of macOS are secret. So Apple goes ahead and patches the apps to maintain compatibility. In fact, Apple is so secretive that it may never tell the app developer that their app has been patched by the system frameworks, much to the frustration of the app developers themselves.
What actually happens is this: Apple works in secret on the next version of macOS. Apple makes changes in the next version of macOS that break an app on the internal list of "do not break" apps. But Apple can't tell the app developer about this, because the changes in the next version of macOS are secret. So Apple goes ahead and patches the apps to maintain compatibility. In fact, Apple is so secretive that it may never tell the app developer that their app has been patched by the system frameworks, much to the frustration of the app developers themselves.