Most people who think about this stuff often seem to think that TAO already has access and the only purpose is to create a precedent to use this legal process against anyone.
There are dozens if not hundreds of viable methods to obtain this info, FBI is choosing to pursue the court order route instead of any of the other forensic tools available to them.
The simple fact of the matter is that the encrypted data and the key to decrypt it both live in a piece of physical hardware on the device-- no matter how well obfuscated it is, it can still be analyzed and recovered by a sufficiently advanced technical entity.
This is exactly the type of work that NSA TAO exists to accomplish, and they are widely regarded as one of the best organizations of this kind in the world.