Disagree, it easily does 9km/L in stop and go traffic. Regularly do it on congested roads.
What kills the average further is if you keep the engine running when idling. Stopped somewhere for a few mins for any reason? Switch off the engine.
Another thing that ruins the average is if you take a long time to “warm up” the car at cold start. Don’t do that and it’s not needed, as long as using 0w20 to 5w40 oil grades. Start the car, wait 20-30 seconds and start driving gently. In winters may give up to a minute max.