"Not yet optimized with Android" would refer to stuff at a system level, various peripherals on the SoC, power management, maybe some aspects of GPU support and integration. It's not going to be about CPU performance. All that optimization they already did for x86 carries over there. Sunspider scores are so different because the browser is totally different and it's highly dependent on browser, this is nothing very new.
This probably also includes Dalvik optimizations, which could affect alleged "CPU benchmarks."