This is not true.
Guys, the reasonable default is not "yeah this sounds similar to what EY said once," but "I don't believe you."
Are you just stating that that the upper limit is not 4? Interesting - what is it and please estimate how rare the ability is. Is there anything else unusual about these people?
http://www.johndcook.com/blog/2013/02/04/four-hours-of-concentration/
And since this is the Internet, and facts are involved, our gwern turns up there also.