Apple makes sure an app cannot get data outside its sandbox without your permission, but it has no control over what the app does with its own data. For example

Apple makes sure an app cannot get data outside its sandbox without your permission, but it has no control over what the app does with its own data. For example, I've backed up and synced data with a server on iOS apps without needing any special permission from Apple or infringing AppStore policies. What you're describing here is not really related to the App Store policies but your trust on the Apple apps themselves.