Exactly. Perrilloux got the late-game drives and two starts when Flynn was hurt, exactly as a reserve quarterback is expected to do. The spot substitutions are a part of the modern offense where coaches often substitute specific players for specific plays, specific situations, or against specific opponents. LSU was fortunate to be able to do this last season with the quarterback, too.
I agree that running the offense was the primary reason, but game time experience had to be a factor.
It'll be interesting to see if the coaching staff continues to roll in the 2nd string guy this year. We didn't do it with Flynn when Jamarcus was here, but it was a different coor.