Almost all PC games now have an auto calibration button.
It's pretty easy to measure the systems FLOPS and amount of memory and calculate the best settings.
Look at Tera for example which has both an auto calibration button and different settings 1-6 from low to maximum settings.
Any developer worth its salt would customise the engine for each platform, limiting the PC game engine based on how a PS3 renders and processes data is asking for trouble.This is never easy to do successfully with multi-platform games.
Because it is being released on PS3, it is FORCED to use a lot of CPU rendering.