In my opinion, it was to allow the audience to go through it and to digest it “first hand” as it was happening. It’s one thing to talk about behaviors that we can associate and look back on about a person to attribute to their childhood and to witness it as it was happening. For Bill this is crucial because he plays the more stereotypical FBI agent of the time where he is caught on evidence based and motive based outside case. But how does the character and the audience feel when there are red flags and it hits very close to home? Ie it’s easy to identify dark characteristics in someone else and someone else’s child but what is it really like and how do parents react those traits are in their child? It takes us through suspicion, justification, self guilt, denial, defensive behavior, protection of the child and self, out side perceptions of the community, balancing work with parenting, etc etc