Earlier quoted context omitted.
But then the best extroverts will want to work with the best introverts and vice versa, so the introverts still have to "sell" themselves!
Or the best extroverts will seek out the best introverts. If you are selling something, you want to sell the best product around - it makes your life easier - so you find the best possible thing to sell.
Right, but how do they know who the best introverts are if the best introverts are not marketing themselves in one way or another?