There is something voyeuristic about how the creators portray the subjects in the story. For most of the subjects, they signed off the same way that anyone signs off on being portrayed in any piece journalism (I presume). But for John B, a lot was revealed about him posthumously, which I think we have good reason to believe he wanted to keep private; he explicitly glossed over (lied about?) aspects of his life, like "church", implying that he did not want to publicize this side of him.
At a higher level, I wonder if the fact that this is more narrative, more art, changes what the signoff requirements should be.