I don't get it.....How could the bearings run that high above the fork crown?? I never encountered a lower race that would be that thick. Was the lower race properly installed? did it sit right on top of the crown or was there a gap between the top of the fork crown and the bottom of the lower race? I'm also wondering whether someone at one time installed too many bearings at the lower race that made one or a couple of the bearings ride above and outside of the bearing race, causing that groove after some time.
Thing is, what ever caused that groove has now developed a weak spot on the steerer tube with that groove. It could act like a stress riser and eventually crack where that groove is. Prayers might be a good idea, if you plan to continue using this fork....

Chombi