Earlier quoted context omitted.
"The evidence we received" is fairly meaningless when coupled with "we weren't allowed to obtain the evidence we wanted ".
I've lived through an IG investigation. You generally only want to respond in writing so you give a correct and complete answer instead of misspeaking and having it used against you, your project, or agency later on. It doesn't hold the legal consequences of screwing up an FBI interview but can be devastating professionally.
Senior Defense Department officials were barred from answering questions on the subject during interviews