The planks are split with an axe or hatchet. Using the knife to split the splints is MUCH more controllable than using either an axe, hatchet, or conventional knife. You can readily position the blade right where you want it, then use smooth continuous pressure and intermittent twists to guide the split. Makes getting nice thin splints for the initial fire starting very easy. A hatchet or regular knife works fine for the slightly thicker splitting, but for this kind of material and the stage at which you use it in fire starting, a little difference in thickness makes a big difference in how readily it ignites.
How different do you think these are from a "real" draw knife?