I would really be surprised if the excluder had anything at all to do with the cross comb. In a foundationless box, one really needs a frame of drawn comb or some foundation to try to give the bees a direction or at least make it easy to go in your chosen direction. If you can put a foundationless frame between two drawn combs, especially capped brood comb, the bees tend to draw it very much to your purpose. I seldom use excluders except when producing comb honey or for splitting a colony. If you don't have some drawn comb above the excluder, they can act as a barrier that your bees may not cross.