I don't think the label of introvert or extrovert, no matter what the definition, can describe a human wholly. We all have tendencies. I think if you tend to be an introvert by your actions than you are an introvert. For those, who claim to be introverts and are extroverts, they may be more likely seeking attention and/or are types of performers than the typical introvert.

You might be interested in learning more about the Kolbe ($$) test. It is better than the well-known Myers-Briggs test.

http://kolbe.com