The graphite marker is not set in wood, but only lacquered on the outside so that the graphite does not rub off on the fingers while drawing.
The graphite lead can be sharpened like a pencil with a sharpener or sandpaper, but this is not necessary.
During drawing, the lacquer layer on the top of the graphite marker also wears off, allowing you to continue working without any problems without sharpening the marker.