Not necessarily
One of the problems of sending in someone under cover is that they have to be convincing enough to be accepted as the genuine article. They also have to be able to keep their wits and gather pertinent info without "going native" as Walker apparently did. It's one thing for the FBI to infiltrate someone into the Mob, and even that's difficult. It's another thing to get someone into an organization where religious devotion must be absolutely convincing and you might be called on to do some very unsavory things to avoid blowing your cover.