First, let me say that I'm not attacking you. I'm merely offering an alternative to what you're saying.
You say, that the parents did not, over the years, ask him leading questions. How do you know that? Were you present for each and every conversation they had?
Or, are the parents saying they never asked leading questions?
Can you see the difference? One is an eyewitness account and the other is hearsay based upon what you read in the parents' book.
I spent most of my adult life as a psychologist/counselor with a PhD in Clinical Psychology.
It was my professional task and skill to distinguish between delusion, deception and truth.
I have not a shred of a doubt about the assertions in the book.
Not a shred.
Evidently, you have not read the book.