Depends, its complicated: There are a lot of people who are introverts to different degrees, and there are a lot of people who have introvert traits to differing degrees. How people would react to whatever happens or whomever depends on the circumstances, the person and everything that could affect their introvert trait. An introvert is not introvert in all circumstances, and people who have introvert tendencies can selectively exhibit that depending on circumstance, how well they know someone and many other factors.

But the biggest problem comes from the stress that people experience in the modern society. From economic insecurity to social/psychological problems, large segments of the population in the West are perpetually stressed, and this causes major estrangement and antisocial behavior in many people. Before we had introverts, people with introvert tendencies. But now everyone is antisocial and closed to varying degrees.

Long story short, maybe such criteria would be useful in earlier decades, or actually maybe the middle of the last century. But in today's psychologically disturbed climate, its really a crapshoot.