Apple strives to make devices that they themselves cannot break into. It started with the iPhone and is now in the iPad, Watch, and some of their computers. Recent breaks were possible through flaws in the iOS, that Apple promptly fixed. If you read and understand Apple’s security overview, the newer phones are closer to Apple having no access.
Previous phones with the “secure enclave” had their unique identity (UID) key burned into silicon during manufacturing without leaving a record. Because the UID was immutable, it was conceivable that the iOS could be replaced with a specially crafted version containing weakened security.
The UID is the source key for all subsequent encryption, leaving it possible to get at data after replacing the iOS. Now the UID is generated by the iOS upon its first start. That makes it trickier to replace the iOS without changing the UID key. If that key is lost, all the data remains forever inaccessible.
Time to work those bitcoin encryption magic into devices.