I thought it was a machine error, too, but Google assured me that they had people doing this by hand. In some cases, they got their metadata from a provider in Armenia. They say that they want to have a diversity of sources to get a more complete classification for every book, but that’s just silly. The metadata at the Harvard Library was done by hand by smart people who know how to catalog.
People at Google are also saying, “Let’s crowdsource this,” but that is a stupid idea. You and I are both smart, knowledgeable people, but I wouldn’t trust either of us to do the skilled work of cataloging a 1890 edition of “Madame Bovary.” It’s very difficult. It has to be coordinated by uniform standards. An example of the kind of mess you get when you don’t use uniform standards is Wiktionary (the lexical counterpart of Wikipedia). Unlike an encyclopedia, a dictionary isn’t useful unless it’s consistent in style. And metadata is hard to fix if you don’t get it right in the first place. Someone has to spend a lot of money to properly catalog a research library, and I don’t know if Google understood that going into it.