Introversion is a personality factor which is at least partly explained by biochemical make up. Neurotransmitters are chemicals we all have inside us. Two which are highly relevant to introversion and extroversion.
Dopamine helps us prepare for time with people and challenges. Introverts are more sensitive to it than extroverts, so get tired around people more quickly
Acetylcholine increases alertness and blood flow to the prefrontal cortex, where introverts have thicker grey matter. This is where abstract thought and decision-making are seen.
So introversion / extroversion is real. Introverts going to find some things harder than extroverts and be better at others. A good leader will help their whole team work on their joint strengths.
How do you lead people to get the most from all of them?