I, myself am an ambivert. On the MBTI it is shown with an X. An interesting article and I thank you for writing it. When describing introversion and extroversion; it’s really not that introverts are shy and extroverts are loud and rambunctious~ though, it could be the case. But rather, it’s all about the energy.
Let’s use the metaphor of the cellular phone battery. The introvert is recharging when s/he are alone or with maybe one other person. But their battery is being drained when they are in a large group setting. That is why they may want to retire early. On the other hand, the extrovert’s battery is being drained when s/he is alone and being recharged when with a large group of people. At midnight, they most likely are feeling energized and want to continue with the group for a while longer. It’s where the energy is~ is it draining, or being replenished, that is the real issue.