I'm completely speculating here, but I imagine that Zynga didn't really care too much one way or the other if this guy took the job or not. Assuming that they're probably primarily interested in Draw Something, and given that this guy didn't work on Draw Something, then this guy is just another random programmer as far a Zynga is concerned. Had he been the inventor and lead designer of Draw Something they probably would have been more open to negotiation.