The black olive in the mole with pork adds a nice flavor to the tamale.
Funny story, a couple years back I made some tamales when I lived in Colorado and gave some to my neighbor to taste. He came over the next day with a funny look on his face like he wanted to tell me something but wasn't sure how to bring it up. Finally he worked up the nerve to tell me that he thinks I accidentally dropped an olive in the tamale. I said, "Olive? What olive?". He turned kinda more pale then he already was. Big swallow, he says "there was an olive in the tamale.". I laughed and said "that's not an olive that's a cockroach! It's an authentic mexican tamale!". He believed it because over the years I had already fed him menudo and tripas at my place so a cockroach wasn't too far fetched! I think he wanted to pass out then I told him the truth that I meant to put the olive in there. It look him a little while to compose himself but we laugh about it now.