I think the issue is some people have somehow set the game to the incorrect title.
As far as I have seen it, most of the platform is built around games using string identifiers, where incorrect strings count as unique games.
You can see the behaviour on the site as well by checking http://www.twitch.tv/directory/game/Dota%202 versus http://www.twitch.tv/directory/game/dota%202
I have seen the same thing happening for Arma III (listed as “Arma III” by default, but someone streamed with “Arma 3” instead) The API seems to allow any string.