To get immunity, you have to proffer what evidence you have. So the IT guy had something valuable or they would not have given him immunity. You don’t get blanket immunity and then they ask you what you know. You have to tell them first.
Yes, and that is my point. He knew and could verify lots of things which greatly accelerated the FBI’s work and gave them insights into who did what. I don’t think you can overstate his value to the investigation. And the FBI had a lot of leverage with this young man.