Rabbits

Hello fellow rabbit people - has anyone else noticed that if they scratch on their bun's lower back that said bun starts grooming? It feels exactly like when a dog's hind paw starts shaking except she turns and grooms her shoulders. It's super strange. She doesn't seem to hate the scratches (above her tail, in a region she's always a little scruffy in because I don't know if she can reach as well back there in her old age). It's just the strangest thing and I don't know if it's a sign of something.