Yeah read about that "Most unfriendly city" too and its misleading since people aren't unfriendly, they're just not as chatty as in other countries.
People here are friendly and very helpful, but they aren't talkative. Austrians are very withdrawn and xenophobic in general, but if you're a tourist and ask them something, they'll open up and will be more than happy to help. If you start talking with a random stranger about anything in America, he'll gladly join the smalltalk, if you do that in Austria, people will kinda answer but also think "wtf why does that guy talk to me like that I dont know him". As long as you don't need help with something or are in an area that invites to talk to people (like at the moment the christmas market), its kinda unpolite; people like to let others bother with their own stuff. If you want to talk to people you go to places like pubs, markets, etc which are "dedicated" for that. It's kinda nice because if lets you choose if you want to socialize or be unbothered, I understand that it's an odd experience for people who don't live here.
I guess a big part is also the classic viennese humor, which consists of nagging about something in a half-serious-half-comedic matter with lots of (self-)irony and cynism, called "Wiener-Schmäh" and it being misunderstood by people from outside. People like to rant a lot and not really mean it.
All in all I think when most people here heard that Vienna is one of the most unfriendly cities they were like "Hahaha. Good
"
Also, talking about people being made out of stone: go to Salzburg, people there are even more withdrawn, and I say that as a native of Salzburg. Not unfriendly though, just not very easy to start conversations with. I'm slowly starting to understand why the Japanese like us so much and visit so often, we're pretty similar when it comes to personal distance and politeness in public.