This is not something I’ve ever noticed. I almost feel tempted to find a belly button to sniff, but that might just be due to the large number of martinis I drank tonight.
However, if you really think about it, ears and belly buttons are both areas where dead skin cells and dried sweat can accumulate. If you have a deep “innie” as opposed to an “outie,” and aren’t careful to thoroughly clean it, I guess it could end up smelling like someone’s unQ-tipped ear canal.