Why can't I create some units?

On Falnass I desperately want to build Smarties, but they are never available.  That's puzzling since they aren't high level units and I think they appeared in every previous map.  This seems like an arbitrary deletion, maybe done to balance the sceneario somehow.  But it is frustrating, partly because it seems to make no sense and partly because there seems to be no good substitute.

Thanks!