If I was the NSA, I certainly wouldn't be exposing the fact that I could crack AES for the sake of a trivial (to the NSA) crime like this.

What I would do, however, is engineer a situation where the FBI could believably brute force the password, then let them have at it for a few days until I supply them with the actual password. Then the FBI tells the public that the passphrase on the phone was actually something trivially guessable lime 000000.