I didn't see the question, but I think you may have read it wrong. I can only name 5. Drew Brees did it in two different seasons, though, so maybe they counted him twice. I'm thinking it may have been "It is only the 6th time in Big Ten history a QB has thrown for 500+ and 400+ yards in a single season."
Drew Brees, Purdue 1998
Drew Brees, Purdue 1999
C.J. Bacher, Northwestern 2007
Devin Gardner, Michigan 2013
Chuck Hartlieb, Iowa 1988
Dave Wilson, Illinois 1980