The government article I linked mentions agents and prosecutors and recordings separately. After reading around a bit, this is all immensely complicated. Much of the data involving prosecutors and agents has to do with the government not having to record interviews with witnesses, and we know this interview was recorded. (Make that some part of the interview was recorded. We don't know how long they were talking before the recording started. That part would be where the agents fit in.) The next time I get a chance, I'm going to look specifically at Florida and find out if it has any mandatory recording laws.
With regard to a prosecutor interviewing witnesses, it seems logical that someone attached to the prosecutor's office, or the prosecutor him/herself, would have to review witness statements before a trial. After all, a year or two may have elapsed since the original interviews, and they don't want to be asking questions if the possibility exists the answer has changed. There wouldn't be as much danger for a prosecutor to engage in this kind of interview because it would be more verification than investigation. If that is the case, it would mean Una<cough><cough> may have a point.
I put a question in to Mike at the web site that originated the article about that, and hopefully I will hear back from him.