Personally, I believe it's for the bone (or "chewie") to absorb more minerals - unfortunately, the soil is deplete - but I believe the "innate intelligence" of the dogs still "tells" them - Hey, bury this.
There is a name for a behavior animals do who do a lot of chewing when they are minerally deficient: I believe the term is "cribbing"....
As far as the elephant penis goes, if I KNEW it would give me a mineral I couldn't get ANYwhere else and I needed it? ...
...sure, why not?
But then again, my family tells me I would eat anything!
In my younger years I wouldn't have had ANY problem trying out for that now cancelled show: "Fear Factor".... I've never eaten a spider, but $50,000 would pay off all but my mortgage!!! So, an elephant penis sounds pretty tame to me.