Heard another really good point somewhat backed up by a dev. Dirt 5 devs mentioned something about being able to multithread properly late in the development cycle and how it had a significant impact on performance. If the tools only recently fixed whatever issue was related to that, could also explain frame rates. Chance some of the bigger games simply were not able to perform last minute optimization resulting from tools fix related to multithreading. Might be the best case scenario honestly because that could be addressed by developers the fastest.