I feel like every single reply from them was about whether he held the copyright rather than whether he had the identity he claimed, and part of what went wrong is he kept asking about how to prove his identity in the replies.

I suspect what happened is they had some tag for what the content at that URL was and it wrongly was some other book, so the question wasn't his identity but the content's identity that had to be addressed. Their replies all look consistent with "the book at that URL is not the book you are claiming you own"

Not that their handling was good or clear, but to my eyes both sides were talking past eachother since he kept talking about his identity and the Google side wasn't disputing his identity.