The original article misses the whole point of the NSFileProtection API: the strongest level of protection, NSFileProtectionComplete, prevents access to files while the device is locked. The whole point of the API is to protect things until the user has authenticated. (It's quite possible Mailbox is already using this API, given the evidence presented.)

In other words, this is the expected behaviour when your phone is unlocked.

See: https://developer.apple.com/library/ios/documentation/Cocoa/...