I don't understand the question...

Those three WebGPU implementation libraries are compiled to native code (they are written in Rust or C/C++), and at least WGPU and Dawn are usable as native libraries outside the browser in regular native apps that want to use WebGPU as a cross-platform 3D API.

Yet still, those native libraries do a runtime translation of WebGPU API calls to DX/Vk/Metal API calls (and also a runtime translation of either WGSL or SPIRV to the respective 3D backend API shading languages) - in that sense, quite similar to what Proton does, just for a different 'frontend API'.

Then performance of WGPU will always be problematic, below that of the native APIs (DX, vk and Metal), and constrained within the limits of the WebGPU spec.