Literally every legal expert commenting on this says otherwise. You don't get deals like this until you're in the end game of an investigation and the investigators know what you know already. They don't offer immunity to find out what you're hiding, they offer immunity because they already know what you did and want the higher ups

The whole team of investigators working on this have specialties in dealing with the mob. They were hired specifically to flip people loyal to a crime boss. I think they know what they're doing