We all know that there's a big overlap between liking something and being good at it, and similarly between being bad at something and disliking it. I used to hate running, until I got to be good at it, at which point I started liking it. It's the same thing with social interactions -- people who suck at them will dislike them. If your conversations with strangers are full of awkward pauses and struggling to find something to say then no wonder you hate talking to strangers.
But social skills can be improved through practice, so it's not surprising to see some introverts becoming less introverted as they get better at talking to people.
What I found was that despite me having fun and being confident in talking to people and interacting in group activities, there's just comes a point in my day where I literally just don't want to talk to anyone. Socially (and even physically, albeit to a lesser extent) speaking, I'm completely and totally drained. It becomes almost painful to engage in conversation that I feel isn't too useful or too interesting. And honestly, I kinda want to be left alone so I can just gather myself. Sometimes I need a day, sometimes a week. But ultimately, at some point I need time to recover from the social stimulation of my day.
From my experiences, I think that's where a big divide between introverts and extroverts exist. To the extrovert, when an introvert gets into his/her shell so that they can recover socially, it appears as if they may be aloof or bored with you, when in fact, they're just tired. This is especially irritating with friends who constantly ask me if "I'm okay" or if there's "something wrong". They don't understand that I'm comfortable with silence and for large parts of my day I actually prefer, and it has nothing to do with them.
Also, just a side note. Something I found quite funny is that because I feel that I'm an introvert and had to struggle with social anxiety through my teenage years, I now feel like I have to overcompensate in social settings, so I'm generally the one who leads a conversation and pushes it forward. I wouldn't be surprised to find out that there are others who also do this.
I think to an extent, we're debating the semantics of "extrovert".
I don't know if "fix" is the right word in the complete, but they can definitely change. I used to follow that list pretty closely - and while there's nothing intrinsically wrong with that, I realized that it can be extremely socially disadvantageous. Regardless of how smart someone is, it's an undeniable fact that in this world, almost all the time, you need the support of other people to make your desires come true. I'll cite the academic community on this one: even if you make a great scientific discovery, you'll never get a Nobel prize if all the other academics think you're a jerk.
I really think the primary talent any intelligent person should learn is adaptation - and that includes adapting to your social surroundings. For example: although I played a lot of sports semi-professionally, I have never enjoyed watching sports... especially team sports. Yet, when I go to a hockey game, I make a ton of noise, and force myself to get into the spirit and have a good time, even though I still haven't bothered to learn the rules.
Don't like idle gossip? Well, it's the fastest way to permeate a new group of people. Now I'm an active gossip and drama seeker (although I make sure the gossip is harmless).
In any case, I feel his point needs to be refined a bit.