Also tbf, the WebGPU peeps did a lot of investigations for what is the actual set of common and web-safe features across D3D, Vulkan and Metal, and all those investigation results are in the open.

In that sense the WebGPU project is an extremely valuable resource for other wrapper APIs, and saves those other APIs a ton of time.

Yeah. SDL went the path of "wrap native APIs". WebGPU went the path of "exactly what level of floating point precision can we guarantee across all APIs" along with "how do we prevent absolutely all invalid behavior at runtime, e.g. out of bounds accesses in shaders, non-dynamically uniform control flow at invalid times, indirect draws that bypass the given limits, preventing too-large shaders that would kill shader compilers, etc".

WebGPU spends a _lot_ of time investigating buggy driver behavior and trying to make things spec-conformant across a lot of disparate and frankly janky platforms. There's a big difference between writing an RHI, and writing a _spec_.