pg isn't saying that your team is flawed - he's talking in general, and in a statistical sense. People who start out as friends before are more likely to succeed - that doesn't imply anything bad about your specific group. I think at the level where you're "interviewing" thousands of teams, looking for patterns starts to mean a lot.
I'm working with some great folks now and we simply started by trying to build something. We're still in that mindset. We didn't start out as friends but after eight months, we are. There's the pressure to get stuff done because we don't want to let each other down. We laugh more than we disagree. It feels like the friendships and the startup are growing together. I have a hard time thinking that the team could be flawed because we didn't start out knowing each other well.