The only reason I can think of that could be called supportable to avoid recordings in closed FBI questionings would be in the case of national security, such as if information that should not be made public is required to be submitted to the FBI in the course of an investigation. I could understand that, although arguably it could still be recorded and just redacted if the recording is ever called upon. Since national security cannot have been the reason for Hillary to set up a private server this scenario therefore doesn't apply here, but I guess it's still possibly in theory.