I don't believe that. I know something about hacking, and I find it hard to believe that anyone could make hardware or software so clever that it cannot be hacked. Look up how various people all over the world broke the high level of encryption of Satellite receivers.
They literally removed the epoxy covers of the I.C. chips, (Called "Decapping") and made contacts into specific points on the I.C. Substrate.
If it were not within Apple's capability, they would not be making a fuss about it. They would simply say they can't do it. No. They are making a fuss precisely because they know they can do it.
The judge has ordered them to divert manpower and resources into developing that capability.
For which they can legitimately bill the government for their costs. Work on their IPhone XX can wait for a couple of days.
You surely do not think the government will never ask them to use that capability again.
No, I expect the government will ask them to use that capability quite a few more times, and I expect so long as a demand from the government is accompanied by a search warrant signed by a Judge, they will have a legal and moral responsibility to comply.
But they have a right to keep the process proprietary. They have a right to keep the government from being able to do it at whim.