I know dogs will chew on rocks when they are bored. Perhaps he wasn't getting enough attention and exercise in his last house.

As for even wear it depends.... some dogs chew more on one side than the other. And dogs can break their teeth on rawhides... I think that has more to do with genetics and chance....

Ramone (my rottweiler boy) is an avid chewer period. He has all sorts of bones and chew toys that he uses that the shelties don't even look at. I bet if all he had as an option to chew on were rocks then he would definitely chew on them.