I wonder why that is? Probably some sort of politically correct fantasy. I did a googlethespys search and have found the name Usama linked to many other names but not to bin laden. In fact googlethespys automatically changes the search to Osama.
Here is a 2003 news article from Fox News that mentions “Usama Bin Laden”.
http://www.foxnews.com/story/0,2933,100021,00.html