They have <iPlacementOrder>-1</iPlacementOrder>, it was done so they don't spawn on earth, if someone does crazy things with SmartMap resource generation....I have tested the 'Randomize Resources' function and while it seems to work fine on terran tiles there are issues in space. I only got a few resources on the moon (Iron, Titanium, Bauxite) but nothing else outside of earth. Compared to the Large Spacemap in its original setup there are 13 space resources missing. Therefore I can't recommend this function with spacemaps.
I wonder if @Toffer90 can limit them so they don't appear on Earth tiles.