For a slightly less tolerant review of the app's behavior (generally, and on Hemingway specifically) check out Mark Liberman's take here: http://languagelog.ldc.upenn.edu/nll/?p=10416
I applaud Mark Liberman for the tag "Prescriptivist poppycock."
I still wait for somebody to actually pass one whole Hemingway's novel through the app and tell us about the results. Probably the new insights await us, once we analyze the dynamics of the "badness" inside of the real novel.