not sure....I notied this also on my Lobots, but not on any other (that comes into my mind right now).
Dont start with Leia bespin...this is the most complicated figure regarding mold, spray masks and coo.
Most spray varaints on one coo really are the result (as AJ mentioned) of "wider" or "closer" sprayed.
But on the Lobot there is really 2 different spray amsks used on the face IMO.....and the small and large squares on the back to go with tem it seems!
Im really just talking from my mind here!.....could be mixing things up.....though