I didn't know that but given the fighting I've seen over credits I am not surprised. I tell the story of the little man who fought like a demon to get an EP credit on a small film based on the fact that two years earlier he had introduced me to a guy who later introduced me to the guys I was going to partner with on the project. He made a real pain in the ass of himself and burned every relationship before he settled for a 'special mention' right before the financing fell through.
Yeah, it's all about credits. One of the busier sections of the Writers Guild is the one that does credit arbitrations, trying to figure out who among the writers, re-writers, punch-up writers, and rewriting director actually made the largest contribution to the finished product.
Since Producers don't have a formal labor union, it's pretty much a free-for-all.