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By default, the Photos folder exists at /Photos, so that DBRoulette example will only work for non-app folder permission apps, since app folders exist at /Apps/{app folder name}. You can create a Photos folder inside /Apps/{app folder name} manually though, e.g., via the web site.

Anyway, sample app aside, the "My app only needs access to files it creates." selection results in your app having the app folder permission. When a user links an app with the app folder permission to their account, a special app folder is created in the account, under /Apps/. The user can add any files or folders in that app folder and the app will be able to see them.