The cat uses trees, as stated, as many things but here it would not uncommon to see the oak as the marker, not the stone. Cats would spray the tree, not necessarily the rock. A rock as a further marker would be a non-essential redundancy that a cat would more or less ignore. It would be like saying one needed to ignore the law of God (written on the stone) to honour their promise to not honour foreign gods. The human reaction of obvious strangeness would begin here. If the tree is seen as an item to climb, the rendition would get more queer to the human interpretation.