Valve's SteamOS Now Supports Vulkan, The Cross-Platform Alternative To DirectX 12 (pcworld.com)
SteamOS just gained support for Vulkan, the cross-platform alternative to Microsoft's DirectX 12 and Apple's Metal. This should make it easier for developers to write and optimize games for SteamOS, closing the performance gap with Windows and encouraging more developers to support Linux. This feature arrived in SteamOS Brewmaster version 2.63. Valve added version 355 of the Linux Nvidia driver, which means SteamOS offers Vulkan support when used alongside Nvidia hardware. Intel's graphics hardware should also support Vulkan on SteamOS in the near future. AMD is still working on its new driver, known as AMDGPU, that will replace the current fglrx driver for SteamOS and other Linux-based platforms. If you use Linux distribution besides SteamOS, you can download Nvidia's Vulkan-ready Linux driver or an experimental version of Intel's Vulkan-enabled graphics driver.
an OpenGL emulation running on top of Direct X, as is done on Windows
Stop spewing bullshit. Windows provides a user mode thunk layer to allow installable client drivers (OpenGL, OpenCL, Vulkan, Mantle) to communicate with WDDM kernel mode drivers.
there's no unrolling layer between the instruction stream and the card to protect it.
I've worked on graphics drivers for 3 major vendors, and every one of them can and does unroll loops in OpenGL shaders. The actual situation is complex for both DX and GL, as it involves a myriad of factors such as the version being targeted, whether the loop bounds are statically known by the compiler, and whether they vary per SIMD-channel. Furthermore, GL supports device restart on hung shaders, and this is tested for in many common test suites.
So, your post is almost entirely incorrect. Charitably, we can chalk it to innocent ignorance rather than a vested interest in spreading misinformation about platform-independed APIs.