Locked chocolate squares restrict the board. However, only locked chocolate squares on fourth row can spread because locked chocolate squares on sixth and eighth row are blocked by conveyor belt, so they will not spread.
The orders are worth 20,000 points. Hence, an additional 10,000 points is required to earn one star.
The locked chocolate is merely a temporary impediment - once you fire off a couple of special candies and then use the helpful converted mystery candies, the order resolves very quickly with limited need for thought and certainly no need to worry about spreading chocolate.