I actually read that article last evening. It is a similar argument floated by Jeremy Siegel in the past. My view is that it is revisionist thinking and agree with John Hussman that the median valuation of domestic stocks are at the highest level ever. For his research on that see his Weekly Commentary 10/3/2016. He Tweeted this comment on the article you linked article a few hours ago:
"Adjusting the CAPE for systematic biases relevant to subsequent market returns, it would now actually be 36."