That's pretty much it. It's a compliance-type regulation. The idea is that if you were, say, hiding a $3bn loss in an obscure book or something then it is more likely to be discovered if you were out of the office and someone else is trading/covering your books.

You can read an article about it in the WSJ here: http://www.wsj.com/articles/SB100008723963904449149045776154... or google for "Take Those Two Weeks Off —Or Else" and click the top link.