Nope that's not true.
It'll alter fueling which is miles better than just running a standard 'map' with mods. It helped my SR when it was setup on the dyno to keep the AFR at the right level to produce more power/torque.
Edit: Probably unnecessary on yours though Tom.
But it will indirectly cause your ignition timing to be wrong, as it alters airflow voltages so the ECU doesn't use the correct timing for the actual engine load, but it will use the ignition timing for the modified load.
It's fine if its setup on a dyno. It's still much better than running a stock ECU/map anyway. The K11 runs very lean in the midrange.