Instead, if anonymity is essential, a generic reference should be used, like "Person 1."
9-11.130 - LIMITATION ON NAMING PERSONS AS UNINDICTED CO-CONSPIRATORS (Justice Manual)....
"Ordinarily, there is no need to name a person as an unindicted co-conspirator in an indictment in order to fulfill any legitimate prosecutorial interest or duty."
Could be that people the FIB has dirt on and has over a barrel to do "informant" work.....to make things happen that the FIB wants to happen, could have one last thing hanging over their head. Cooperate, testify and say what the FIB wants them to say or else "unindicted" changes to "indicted".