I think Tim Cook might be subject to extra criticism for similar reasons.

"I think it's worth noting these little hints that outgoing and extroverted are thought to be synonymous with "good leadership" (in the US, at least)"

I don't think it's synonymous, but it's required. To be a good leader, you need to enjoy being around and understanding people.

Most introverted people don't really enjoy either.

I've had many introverted managers and they all were horrible: lack of communication which went hand-in-hand with passive aggressive behavior.

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.

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.