And your office did a great job ISBing that one and handing it over to us.
If I'd been in your shoes when leadership came calling, I would have quoted the job of an ISB (gather and preserve evidence), and then asked them what was taking their SIB so long...
Regarding who can give privilege, in the ISB phase, it's the BP. In the SIB phase, the SIO, IO, or BP can. And they don't have to actually be present when the request is made, they can provide guidance to the rest of the SIB members conducting interviews.