FBI agents cannot make "deals" with criminal suspects. The province of deal making before or during prosecutions lies solely with the US Attorney's Office. Even pretending that you have the capability of making deals with suspects could damage the prosecution of the suspect so, FBI agents would avoid any talk of that nature.
It is stated clearly that the US Attorney's Office approves a deal. The deal was asked by the criminal, the FBI Agents only acted as intermediaries due to the urgency of the situation.