The option AT FRONT is similar to AT CENTER and forces the tool touching point to be always a fix point on the tool. In this case, this fix point is the beginning of radius of a bull nose tool in the direction of tool motion. All changes to tool orientation are done around this pivot point and this will also cause gouging the drive surfaces. Setting the gouge control is critical to work with this option.
Here you can see the tool touching the surface always with the front.