I fully agree with you about the editors/ghost writers, etc. Perhaps they thought the book would sell anyway, checked out or not? Maybe they're too young to know any different, and assume historical accuracy from such a 'direct source'? Who knows.
And the mistakes WILL be repeated down the years, as you point out. That's probably the biggest shame, because in years to come, researchers/historians/journalists will all turn to this book for verification, and won't bother checking things out fully. We've seen it happen so many times, haven't we?!
The 'All My Loving' thing IS odd, I thought that too when reading it, but as I said before, my feeling is that this book tells a lot (between the lines) about Cynthia herself, who I have always found an intriguing lady, not served well by many Beatle books.