I have driven my Xli (2018 FL) with light foot and managed to get 17.2kmpl Tank to Tank method. Cluster showed 18.4.
This is in karachi and i have shared fuelio screenshots also. So this is not something that can be denied. I have kept Cultus VXL manual, Alto VXL, Vitz and Corolla Xli.
Cultus has best of 22kmpl on the same route, Alto has managed to go to 27kmpl and vitz i have never been able to take it above 16 (it has wider and larger tires).
So it is on the same route, same season and same tank to tank method. Also same fuel outlet and aut nozzle stop.