I don't even think there's social pressure to go to lunch. People do because they enjoy it. Sorry if this wasn't clear from the article. It's not a weird cult where I'm forcing introverts into cult-like hanging out with people that they hate or already spend too much time with. That would be inconsistent with our goal of making a humane, friendly, and fun workplace, which was the point of the article.
We very rarely talk about work at lunch. I've never met anyone who visited us for lunch and thought that it was weird. I have met some pretty anti-social people in my time and some of them work for us and somehow they don't seem to mind sitting at the table during lunch and listening to everyone else enjoying the conversations.