If you truly believe that, I think perhaps you place too much trust in the wrong sort of people.
The reason why I consider the hypothesis unlikely is not because those involved are unwilling to deceive, but because they are unlikely to have sufficient skill to make the attempt and avoid detection. I believe that, considering the number of people that would be necessary, at least one Apple insider with ethical concerns would leak evidence that would expose the true story.
I believe that much more than "law enforcement never lies", but IMO it's hard to leak evidence in this case. A whistle-blower could say that he worked on this project, but there isn't the hard evidence of documents that for example Snowden could leak. The FBI or Apple could just deny it or say no comment.
The reason why I consider the hypothesis unlikely is not because those involved are unwilling to deceive, but because they are unlikely to have sufficient skill to make the attempt and avoid detection. I believe that, considering the number of people that would be necessary, at least one Apple insider with ethical concerns would leak evidence that would expose the true story.