Unless there's an incredible amount of people "not in" on some universal secret, maths gonna maths, and physics gonna physics. Actual encryption works well in a proven way, computational power isn't as infinite as some people think, and decent software implementations exists.

Getting hold of anything properly encrypted with no access to the key still requires an incredible amount of computing power to brute force. Weak/bad implementations can leave enough info back to speed this up, malicious software can make use of an extra, undocumented encryption key, etc. but a decent implementation would not be easy to break in.

Now, this does not say anything about what Apple actually do. They claim to have proper encryption, but with anything closed source, you only have your belief to back you up. But it's not an extraordinary claim to say that this can be done competently. And Apple would have a good incentive in doing so: good PR, and no real downside for them since people happily unlock their phone to keep their software running and doing whatever it wants locally.