One detail left from the analysis: these guys are already well-known for their UX work amongst the crowd most likely to purchase Flow.
Reminds me of when Guy Kawasaki launched Alltop for "only 10K." Yeah, 10K + 500K worth of PR that comes with having an enormous following.
This is not to diminish what Metalab or Guy Kawasaki do, I'm admire both. But it's not like these results are as reproducible as they infer without significant connections.