The article does not make clear if the single player aspects of the game were running on the now defunct servers or not. There's a pretty big difference in "DRM" and "requires remote hardware running server code".
the article said the game had always-on drm, even for singe player game. The company who made the game shutdown the servers, making it impossible to play either multi- or singleplayer, so valve simply removed a non-functional game from the library