How do you know if someone selling you something is introverted or extroverted, unless of course they're your friend? All i see is someone trying to pitch somet

How do you know if someone selling you something is introverted or extroverted, unless of course they're your friend? All i see is someone trying to pitch something to me. They could be extroverted and naturally good at it or they could be introverted and acting the part out. How would you know? I'm an introvert myself and if you see me in social situations you'd never think that I am and most people don't realize it until they get to know me personally. This is why this article makes little sense to me.