I think it's a mix of outdated information, wishful thinking, and the contrarian appeal. It was true for a few years that a grandmaster or a random chess player

I think it's a mix of outdated information, wishful thinking, and the contrarian appeal. It was true for a few years that a grandmaster or a random chess player with good 'mechanical sympathy' could crush a solo chess engine (which is why discussions of this tend to stop in 2007 despite being a decade ago), it would be very convenient if AIs required humans for the best performance (https://github.com/JackToaster/Reassuring-Parable-Generator/tree/master https://github.com/JackToaster/Reassuring-Parable-Generator/... 'A computer will never play the best chess in the world'), and it provides a meta-contrarian (http://lesswrong.com/lw/2pv/intellectual_hipsters_and_metacontrarianism/ http://lesswrong.com/lw/2pv/intellectual_hipsters_and_metaco...) take on AI risk/technological unemployment which is clearly Tyler Cowen's main motivation in popularizing it (object: 'AIs will never be able to do X better than humans as they have no soul'; contrarian: 'they totally will, just look'; meta-contrarian: 'ah, but the human element is still critical for a last bit of performance due to the creativity and ingenuity of the human spirit!'). It's also interesting in that it demonstrates that there's at least two levels of 'superhuman' performance in chess and other domains: there's superhuman in being able to beat any living human one on one (Deep Blue, Sedol AlphaGo), and superhuman in being unable to be improved upon by a human collaborator (post-2013 chess engines; AlphaGo Master?). I'm not sure this gap was really expected, but though it only lasts a few years (or months), it's still interesting to note.