There is no such myth. Until seeing this headline (which is linkbait, even after the title change by dang of the HN moderation team), I had never seen the term "massed practice." That's not the term in the scientific literature on the development of expertise. The term in that literature is "deliberate practice," and what deliberate practice is gets a lot of detailed description in that literature.[1] Even the example at the beginning of the article is contrary to the spirit of the deliberate practice literature, which makes me wonder how well they've really thought about the prior literature.
The byline of this article is interesting: "Peter C. Brown is a writer and novelist in St. Paul, Minn.; Henry L. Roediger III and Mark A. McDaniel are professors of psychology at Washington University in St. Louis." That looks to me like two professors of psychology were hacked off that they weren't getting as much attention as the originators of the deliberate practice research, so they decided to hire a ghostwriter to help them write a popular book. (I could be mistaken about how this collaboration originated.) Anyway, the book is gaining some favorable reviews[2] (with the help of their university press office?[3]), so maybe it will be worth a read for us even thought it isn't really a response to what this excerpt suggests it's a response to. Another excerpt from the book[4] has actionable advice that is quite good.
[1] http://scholar.google.com/scholar?hl=en&q=%22deliberate+prac...
[2] http://www.timeshighereducation.co.uk/books/make-it-stick-th...
http://blog.coreknowledge.org/tag/henry-l-roediger/
http://www.psychologytoday.com/blog/is-america/201404/test-p...
[3] http://news.wustl.edu/news/Pages/26780.aspx
[4] http://www.bostonglobe.com/magazine/2014/03/09/how-learn-bet...