They are taking that into account too.
Where in the article does it say they are adjusting offensive and defensive statistics for strength of schedule?
Just for the heck of it,heres the official NCAA records as to toughest schedule.
One of the 4 teams is ranked #1.
http://web1.ncaa.org/mfb/2010/Internet/toughest%20schedule/fbs_9games_cumm.pdf