For those suggesting he was pushed into public appearance at his mother's funeral, I'm guessing (pure conjecture, like everything else on this thread), that he probably had an epic tantrum about wanting to walk behind his mother's coffin, despite those closest to him doing their best to dissuade him. William then worried about how it would look if he didn't do the same, Prince Philip stepped in and said if they were absolutely sure then he would walk with them to support them. Harry, at 12, was probably too young to process the enormity of the situation. William, a couple of years older, understood more.
It's actually William I feel sorry for in all this stirring by Harry. He lost his mother at a young age too. His whole life has been shaped by his future role. He's had to watch Harry shit all over their shared childhood (Harry's been caught out in quite a few 'misrememberances'), had to listen to his brother pontificating about how awful his life was and it will go on and on and on despite Harry's protestations of wanting a life out of the media spotlight. All Harry (and his wife) is doing is courting publicity and the limelight, a position they are unqualified for apart from the connection to Harry's family.
I should imagine this book will be taken as gospel by some, in the same way the netflix series is taken as a documentary by some. It may do damage. I very much agree with the tenet' never complain, never explain', but I think particularly Charles and William are wishing they could write a follow up....