What you're really seeing is the orientation of carbon fiber plys. Instead of covering the face sheet with one ply, they lay down a number of plys at various angles. If you didn't do this, the disk would only be rigid at angles 90 degrees to each other (in the directions of the weave of the carbon fiber fabric). Zipp uses unidirectional (non-woven, all fibers going in the same direction) material, then lays the plys so that the unidirectional fibers are oriented at about 20 degrees from each other.

This creates the illusion of "spokes". It is pretty apparent in pictures of Zipp and Bontrager disks. These disks have molded facesheets sandwiching a honeycomb material - no spokes, externally or internally.

Looks kind of cool, too.

Nice description, thanks for the reply.

Greg