If this parameter is set to AT CENTER, then the tip of tool is touching the surface contact point. If the tool axis orientation is changed due to tilting options, then the tool will be tilted around this tip point. In such case, the tool and surface are not tangential anymore and tool will gouge the surface. This must be then avoided by explicitly turning on gouge checking and i.e. setting the first gouge check strategy to retract back the tool from drive surfaces.
Here you can see the tool touching the surface always with the center.