Most likely the AI was actually trained on LibriVox, potentially even on largely the same books...
EDIT: The first book on the list https://marhamilresearch4.blob.core.windows.net/gutenberg-pu... is "100%: the Story of a Patriot" and the LibriVox version is at https://librivox.org/100-the-story-of-a-patriot-by-upton-sin...