From the SW website
Are Cous-cous cake and lasagne sheet doritos syn free?
You might be disappointed to hear that they’re not. Because changing the use of a food can make it easier to over-eat, to protect your weight loss they become Synned.
When foods like pasta, rice and grains are used in their original form they’re low in energy density (calories), bulky, appetite-satisfying foods. Pasta, couscous and rice are usually the main ingredient in a meal packed with other Free Foods – giving it sufficient bulk to be satisfying as a meal in itself. However, when ground down, used as flour (like in couscous cake), seasoned crisps (like Doritos) or puréed (like smoothies) they’re often used as additions to a main meal… and on top of your day’s Syns. It is a very effective way of adding a lot of extra calories in a non-bulky way, and as such would then be counted as Syns.