You're making way too simplistic a generalization here. Some sociable people can be sociable and friendly with a group until that group changes and they decide that it no longer fits their morality. They can still be contrarians, and then make waves anyhow. You absolutely don't have to be an introverted, hard nosed loner to end up being a whistleblower or contrarian troublemaker. This sounds a bit more like wishful fantasy for people who are socially inept trying to paint it as more noble.

If anything, a sociable, open person is more likely to have the kind of self assured personality that makes them decide it's not a problem to disagree among their peer group whenever it becomes necessary. Read more history, it's full of troublemakers who were also sociable.