[hanse00]

Leadership is a skill to learn, just like programming, writing, or most other things really.

People who are introverts at heart can learn to become just as good managers as those who aren't. It may come less naturally, I couldn't say, but it's definitely possible.

[aspaceman]

I think their point is that it's a hard skill for introverts to learn because they don't enjoy it. It values things they don't care about (or usually don't). In that way, when you have an introverted manager, it's usually the bad kind.