Not true, they can also be friends with another introvert. One day they hang out after having canceled and postponed a dozen times. They act like they have known each other all their lives and like they talk every day, hanging out together for that day doing things they both like. It's super fun for both and they promise to meet up again soon. After that they both need two weeks to recover from that one day of fun. They barely talk to each other the next three months. Then the cycle of planning a meet-up begins again.

This goes on for years, they are best friends and would die for each other.