You should read the AMD blog post about Mantle 1.0 functionality in DX12, and OpenGLNext(Vulkan).
It is in post number 36 in this thread, on this very page. I will link it for ya, after all:
https://forums.anandtech.com/thread...s-in-performance.2486639/page-2#post-38476182
Read the post, and I see no evidence of any connection with DX12.
Have you actually thought that MS could have been developing DX12 for quite some time, but without addition of Mantle it would not be low-level API?
Speculation is fun, but without any evidence whatsoever it becomes quite dull..
You know why is that? Because Microsoft has something like DX11.3 which has most of features of DX12. Apart from the low-level ones. And all of the features that are missing from DX11.3, are somewhat familiar to those who worked with Mantle feature set.
So no, DirectX12 really has Mantle feature set/code inside it.
The main purpose of low level APIs is to remove CPU overhead and increase rendering parallelism. That's where most of the performance increase comes from with both DX12 and Vulkan. You guys need to get over the idea that
only Mantle can be a low level API, much like some of you think that only AMD can do asynchronous compute.
Microsoft is one of the largest tech companies in the World, and actually have the resources, capability and experience to develop whatever kind of API they want without the need for AMD's input; although to be sure, AMD definitely contributed greatly to DX12, along with NVidia, Intel, Qualcomm and many other IHVs..
If there is any connection between DX12 and Mantle, then AMD might have contributed some Mantle code during DX12's development on their behalf. But this doesn't mean that DX12 was inspired by, or created from Mantle.