I think Yost summarizes the spread philosophy well.
"I'm into monotonous. I want them to get tired of doing it. ... We don't coach the exceptions. We coach what we're going to see 85 percent of the time. We do six things 10,000 times. We don't do 10,000 things six times."
The playbook should be fairly easy to learn compared to a pro style offense. It sounds like it would be simple to stop an offense with 6 plays, but consider how difficult it would be to defend a high tempo, no huddle offense that could run any 1 of 6 different plays out of the exact same formation.