It's based on findings regarding his compensation at GNC, stock options, and a post that someone posted a week or so ago showing that his estimated net worth might be around $30 million. Also, he is not on the Forbes billionaire list.
To be a billionaire requires building an empire from nothing or inheriting one. Only a select few of the richest of the richest athletes, celebrities, politicians, etc have made it to that point. Simply holding an executive level position at a somewhat large company won't get you there.