Some teams have the type of offense where they run their system and if they have superior athletes to the competition, they can’t be stopped. The old Leach and OU offenses were that way. As a result they would run up huge scores. The downside was that when they ran into top teams they had few wrinkles to roll out and were stymied.
Sark’s approach and offense is built heavily on deception, motion, and throwing in wrinkles to find space. So he doesn’t do much against lesser teams because he wants to save those wrinkles for the critical games like OU and A&M, keeping them off film. As a result, they often don’t destroy lesser opponents.
He also purposely gets conservative late in games to avoid low percentage scenarios where the competition comes back to win. It’s why he has so many unnecessary close games. And of course this philosophy is flawed. Playing that conservative actually brings low percentage comebacks into play more than just continuing to beat them down.