I've always just thought my introversion was a preference for working more alone than with group, I'd rather have a one-on-one dinner than go to a party, rather read than attend the circus, etc.; I don't feel it has anything to do with friendliness though. I can have fun at a party, find/"make" smaller groups or individuals to talk with; to me it's kind of like going to the ball game and enjoying the people you are with rather than the whole stadium experience; I rarely feel one with a crowd. I also don't go out of my way to make something groupish happen. I'll go along with a group but don't "start" anything.