it doesn't enable better processing across threads.
the problem today is that multicore games use a lot of one core, but then then barely make use of the other cores. This means for high end CPU's like i5 and i7's games today aren't bottlenecked by the CPU because the individual cores are so fast it doesn't bottleneck the GPU. DX12 will like mantle allow the performance to be spread out across the cores. meaning you get more equal usage of the cores so instead of one core having 70-90% utilization. it's more like 30, 20,20,20. or on more demanding games 50,50,50,50. though that's far in the future, cause that's a LOT of CPU power.
What's the difference on taxing a single core and keeping the other ones idle for something else, versus spreading the load on multiple cores?