Super interesting data points! Just thinking about the world population being 250-400million in AD1000 is a huge change to most people's mental models.<p>However, the basic premise of the article is a bit in question - that GRRM/readers indicate that the world itself is realistic - SOCIAL realism is the more abject term here. Lots of numbers are thrown about in the books - even on a relativistic scale these are (as the post stated) incredibly improbable. But its not particularly important to the enjoyment of the story or the "realism" that people claim to attach to.
The population of Westeros should be zero, as the books assert there have been winters that lasted a lifetime. Unless maybe the living dead count?<p>The books are "realistic" only in comparison to other fantasy. It'd be more valid to call it "less fantastic".
The world is there to build a story on and Westeros is fine for that. I only got through part of the article because the authors complaints about realism fell very flat to me.