I think he’s reminding someone out there:
“I know where the bodies are buried.”
I think he is fearful of being thrown overboard.
He might be trying to remind them how valuable his continued silence is.
This is a total blind guess.
I think you may be on to something. He not only knows the genesis for the Trump investigation but also the true backstory on the Clinton email scandal.
He may be signaling he’s ready to work with Barr.