I cannot get on board with stranger abduction for lots of reasons. But a known abductor? TBH, that makes far more sense, especially when adding in their early statements about "who would hate us?" etc. But I'm not sure how that would tie in with the documentary. It could just be that they're as lost and confused as we are and grasping at straws -- anything that offers hope.
I agree with you about a known abductor.
How could doing the documentary give the parents hope?