Does not necessarily mean mean you cannot get carbon build up in the cylinders. DI engines have carbon in the valve areas but any engine gets carbon build up overtime if a few things are not done. First any decent fuel nowadays has sufficient detergents. Bottle of concentrated techron every oil change. And most importantly is driving the car hard regularly and not many short trips where you do not push the car. Every week atleast once should include a nice open freeway run for 15 minutes with multiple WOT runs. This really prevents the process of carbon forming.
Also one thing that is not preventable is if your car tends to burn a lot of oil as the oil in the cylinders will lead to carbon deposits. Again much worse if you do not really get on the gas often to burn them off.
But overall it is WAY better than DI engines which are a nightmare