The system forgives not the slightest deviation from its pre-defined coordinates (sometimes they differ from visual yellow guidelines)
That's why there's a distance readout to begin with. If the scenery visuals and the AFCAD are not in precise agreement (GSX obviously reads the AFCAD), the distance readout will help.
concentrate on the gestures of the marshaller?
Since the message evaluation comes only AFTER you stop the plane, it's not possible you would lose your concentration when parking because of it, unless your are suffering from a "performance anxiety", knowing that you will be evaluated.
With the latest update, it's possible to turn off the marshaller distance readout, not the final evaluation. Can't you just ignore it ?