It's too long to play uninterrupted (about six minutes). If viewers tuned in during the middle of it, with no overlapping commentary, it would spook a lot of folks.
Exactly.
They specifically said something about how they would describe it, but not PLAY it, as a matter of policy.
I think some kind of "policy balloon" went up at Fox when it became apparent that they are issuing very serious "under duress" statements (and that "policy" may even be governmental, since the statements MAY contain coded instructions for terrorists.)
Anyway, I'm just reporting what they said. Any conjecture on WHY they said it is exactly that -- conjecture. And what they said is that it was a policy decision (not the precise words but that's the essence of it) to NOT play the tape, but to only DESCRIBE what it said (which is what they have been doing in very general terms, which IMO ensures that any coded directives will likely be lost in the paraphrase.)