Gas Mileage - Increase

So I took my MY13 Evoque in to get some items looked at, and they advised there was an update to the ECM/PCM firmware. Since that update, I have been getting almost an additional 60kms per tank.

This is obviously a good thing, but my question would be, how are they able to do that only now, and not do this from the start.

Does anyone know if we can hit back at JLR due to low mileage up until now?