There's probably a fair number of Feudal Worlds that have nothing to do with knight-robots. Knight World is just a designation applied to worlds where robot-operator houses rule the roost. Some feudal worlds were probably judged as not worth restoring Knight capability, or didn't sell their souls and will probably never get their systems back.

I imagine a spectrum of knight worlds from feral (where the knight walkers were found and a few leading chieftains were taught to operate them provided they bound themselves to admech) to industrial (dealings with nearest ad mech forge world on terms closer to near-equals rather than puny feral/medieval vassals)