Apple has provided no way for users to revert changes that are being made in iOS, and no mechanism to recover deleted data. That really bothers me because if an automated system is going to make changes to optimize my data then it’s never going to be 100 percent accurate. Dropbox is really close to perfect these days for maintaining the integrity of my data, but they still have mechanisms to recover files and revert versions.
A Time Machine-like interface which would allow you to recover lost media or revert to previous versions of your library would be nice, but it’s never going to happen. It’s a user interface problem that I don’t expect Apple is too interested in solving. In their mind, they’d rather fix the problems they have and remove any need for a data recovery feature.