That version of events certainly sounds like they did a good thing. Convincing someone to use a fake bomb instead of a real gun is a job well done.
Even if that is true (and, like you, I’m not entirely convinced about the FBI’s commitment to truth) it still reminds me other other cases where it seems pretty clear they* groomed vulnerable people to pad some kind of key performance indicator.
* “They” being FBI agents who are presumably completely different FBI agents than the “they” who were involved in this case
