Maybe, but I'm not willing to dismiss the FBI so quickly. It's possible that they release some misinformation (or incomplete or otherwise misleading information) on purpose, to confuse the enemy and engender uncertainty as to how much knowledge the U.S. government has.
This may actually be a good idea tactically, notwithstanding appearances. But if they're doing this, it has the unfortunate side effect of also reducing American morale (by generating doubt as to the competence and integrity of our officials).
In the old days, I would have agreed with you. After all the coverups they've participated in, I suspect that's the least likely excuse.