when should I use iphone.setnobackupflag

I would like to know when it is appropriate and necessary to use setnobackupflag. My app has the following features.

  1. It can download an assetbundle from a server and store it in cache and in persistentdata folder (same as documents?)
  2. It stores an audio file in streamingAssets
  3. It can store an audio file in persistent data folder (same as documents I think).
  4. It uses playerprefs.

This is what Apple says in their rejection emails:

The iOS Data Storage Guidelines indicate that only content that the user creates using your app, e.g., documents, new files, edits, etc., should be backed up by iCloud.

To be on the safe side, apply it to pretty much everything…