On the contrary. The FBI does not record interviews. The agents do the interview, then go back to their office and fill out a Form 302 with their version of the interview. If what they write differs from what you recall saying, you're the one who will be accused of perjury. Moreover, if you insist on recording the interview, they will refuse to continue the interview. The last thing they want as a recorded interview.
Yes you are correct regarding policy of no recording FBI interviews.
However, Comey was the ultimate authority on what facts went into those 302s to be completed by agents in documenting answers to the FBI softball questions of Hillary.
I suspect that Hillary and her lawyers were given a complete list of FBI questions days before her interview so that she was prepared.
Just as I assume that Hillary and her people will be given all debate questions prior to her debate with Trump.