I’m not calling anyone a liar. Ben is making claims and refuses to back those up with any evidence. It’s Schrödinger’s Truth. It’s in the box but we don’t know. It’s fairly common to want people to cite their sources. We’re not talking about military secrets and troop movements here. It’s the sales data for a company that ceased to exist 30-odd years ago.
I think this would absolutely be true if it were a history book. You HAVE to cite your sources. If it is a primary source, it is stronger than a secondary source. An unknown source is considered unreliable...most of the time.
However, in journalism, you have to protect journalistic integrity, and that means when a source doesn't want to be known, you need to protect it. It is part of the ethics of the entire thing.
The question is what type of book is this trying to be. A history of something, or a report on something?
Sometimes, even history books rely on articles from journals or newspapers, sometimes with those having confidential sources.
Tough call on what to call the book in that light. Still, it does seem interesting, and it is probably one of the most informative books on that time period that has been written thus far. It's a little more information that most have had prior to this, and probably more information all together gathered into one spot than anyone has had before.