Well .. here some facts too ...
There is only ONE Laborer. He spans in the cave near Katta, and than starts wandering around between the east and west cave ..
He is definitly NO placeholder for any other grim here. (so not even fur the runner)
Laborers have approx. 80 % of the time one ore more orepieces with them ... so they are the most worthy orebringers in the zone .. but ... well .. as mentioned ... there is only ONE of him in the zone at a time. But therefore he is a regular spawn, as his path belongs all to himself.