Yes and no: here is a short article about it from Brad Wardell the CEO from Stardock [0]. Vulkan/Mantle/DirectX12 allow the game developer to really take advantage of multicore CPU's. Which is why we see the most gains with these new low level API's for AMD's FX chips because they are better at multi-threaded workloads compared to single threaded workloads like with previous DirectX versions.
A quote from the linked article:
To to summarize:
DirectX 11: Your CPU communicates to the GPU 1 core to 1 core at a time. It is still a big boost over DirectX 9 where only 1 dedicated thread was allowed to talk to the GPU but it’s still only scratching the surface.
DirectX 12: Every core can talk to the GPU at the same time and, depending on the driver, I could theoretically start taking control and talking to all those cores.
That’s basically the difference. Oversimplified to be sure but it’s why everyone is so excited about this.