> The new combined shader will be named "Mesh" shader
It's only new for Vulkan. On Windows and XBox, mesh shaders were implemented couple years ago: https://devblogs.microsoft.com/directx/coming-to-directx-12-...
This new Vulkan extension is a direct copy-paste of the above, leveraging the same hardware.
However, the hardware support for mesh shaders is less than ideal. That thing needs feature level 12.2, so-called "DirectX 12 Ultimate". It only works on nVidia Turing (GeForce 20 series) or newer, and AMD RDNA2 (Radeon RX 6000 series, and current generation of game consoles).
That PS2 coprocessor is similar to a single ARMv7 core with NEON.
Mesh shaders don't run loops for elements of the meshlets, they do them in parallel, on different threads of the same thread group.
PC hardware vendors design their features in collaboration with Microsoft for a specific DirectX version, and then they land as yet another extension on Khronos APIs.
Vulkan didn't make this better, they have gotten so many extensions by now, that they finally adopted the version profile concept that is traditional in proprietary APIs.