You can still enable full disk wipe after 10 failed password attempts[1]. That was available in iOS 7 I believe (but someone on here will correct me if I'm wrong).
The FBI's point is that Apple can update the software on the device to not honor that setting, which means it is not effective against a government attacker.
[1] - http://i2.wp.com/ioshacker.com/wp-content/uploads/2014/09/Pa...