I think the idea is more that following (2), introverts lose energy whilst extroverts gain energy. (1) doesn't really come into it. You are probably extroverted

I think the idea is more that following (2), introverts lose energy whilst extroverts gain energy. (1) doesn't really come into it. You are probably extroverted. But no it isn't necessarily a dichotomy, rather a rough label of how someone responds to social situations. Their actual character will be much more complex :)