R15 renders a different scene, a simpler/faster render. For that reason alone, it's interesting to benchmark it. Results are not comparable to R20. You run the older version for the same reason you run the new one, to compare scores. Cinebench periodically makes a new version usually when current CPU's finish too quickly, or to incorporate newer instruction sets. People still run the version before R15 as well, R11.5. https://hwbot.org/benchmark/cinebench_-_r11.5/
