The tone of this article is really off-putting and I disagree that it's about laziness or something similar. I'm really shy and take a lot of time to think of even a simple reply sometimes, and often end up not replying at all, so this would probably improve some of my communication.
I don't think there is a correlation between them. Rather, I think that if there are two people who have the same level of intelligence, the one who is a better communicator (and this is more often a trait found in extroverts) comes across as smarter because they can transmit their ideas better.