And if my understanding is correct and they listened to the recording under the best conditions available, why was the boss not interested in listening in to such a crucial piece of evidence at the earliest possible opportunity?
As has already been described, there is a lot of work to be done between "listening" to a recording and issuing an annotated transcript. At the very least, timelines have to be established, unclear and noisy words deciphered, and decisions taken on what to omit out of respect for the dead and their relatives.
Knowing that he was going to face the press, I personally am certain that "the boss" did not listen to the recording, and deliberately so. I am equally personally certain that he has a pretty good idea of the contents, and that these will be released when the job is complete.