Seems to me that the article states the obvious. Introverts are in no way lacking ability or capacities for interacting socially. We just prefer to remain reserved and keep to ourselves, we are private people in many ways but that does not mean to the exclusivity of ever being able to socially interact!

Seems to me in a nutshell and extrovert is for the most part outgoing and social in most situations whereas an introvert is only so when the need arises.

Just my 2c.