The term “ritual object” has become an archaeological cliche for items of unknown use. That’s not to say that people in the past did not have rituals, some of which involved objects. In some cases, objects had no clear practical purpose where they were found, yet had deliberately been placed there.
I would say that the rocks we found in burials at Nuvuk fit into this group. They were much larger than the average rock on that gravel spit, so they had to have been gathered deliberately. They were clearly placed in the grave. Why? We can only speculate. They could have been placed by mourners, somewhat like people may drop flowers in a grave today. Or they could have been given in trade for intact items buried with the person.