The three play thing is a little misleading. Last year there was a clip of ole miss which runs one play (zone read) with 4 options; QB keep, handoff to running back, bubble screen, and a downfield throw. Which play is run is dictated by the defense with the QB making the call. That's harder for a defense to prepare for because all 4 plays presnap look the same. And that really is the key- being able to run, straight pass, or play action pass all from the same formation. Same as an inside zone is always an inside zone whether it's run from offset I, single back, pistol, etc. the assignments don't change but the pre snap defensive reads do.