Well, Austrians, much to their national pride, don't really speak German, but they have their own localized dialect forks of it which are more difficult to understand for foreigners who only learned "vanilla" German, so the map is correct in this regard.
It's why Arnold Schwarzenegger wasn't allowed to dub his own American movies to German, but the studios got a German actor to voice him since his Styrian dialect was considered too strong for most German speakers.
Similar with Swiss German.
No matter how well you think you know German, you'll always run into a dialect you won't understand.