You are correct, a torsion box has fiberglass all the way around the core. Laminate skis don't have fiberglass on the sides of the core, just above and below. Tecnically all torsion box skis are a torsion box with the top and base laminated to the box. I don't know how it would be possible to include the topsheet and base inside the box because then you would have a fiberglass base and topsheet.