There are people who don’t mind being alone.
They came from childhood, secure and comfortable, confident and capable. They didn’t need Mommy and Daddy and a gang of peers to walk to the corner. And they didn’t mind being alone.
As teenagers, they didn’t need constant approval and companionship , having no problems with social interactions or themselves.
They could put their thoughts into words and think about them. They can reassess a meeting or event and come to a conclusion. They can listen to the news and check what they don’t understand.
They are focused on their perceptions.
It is not that they are anti-social it is that they are not anti-self.