If they meet each other now, when the Enterprise and Discovery meet, then the book is clearly wrong. Yes, I accept that he never spoke about Sybok, nor about the Vulcan Princess who was Sybok's mother. Sarek obviously lead a very complicated life, which was not at all clear from his first appearance in TOS.
Answering the part about why Spock never speaks of Michael was mentioned in the link to the Alex Kurtzman interview above. We don't need to know, but surely we would like to know. Otherwise, why bring Enterprise into the story at all?
As for the history. History in the future is clearly very important to people. I could cite lots of examples but I have to leave the house. The models in Picard's Ready Room are one good example.