What I know is, sky box is just a cube with normals face inside, pasted with sky texture.
Some gfx card (eg GeForce) say that they supported sky box. What that mean? Don’t all gfx card can performe sky box? It just a cube right?
maybe you misconfused SkyBoxes with CubeMapping, they are quite different, even if they could be used together to achieve a good looking environment mapping (using CubeMappnig for reflection and a skybox for background rendering).
hope this helps