> This is the first time it is possible for Rust host + device across all these platforms and OSes and device apis.

I thought wgpu already did that. The new thing here is you code shaders in rust, not WGSL like you do with wgpu

Correct. The new thing is those shaders/kernel also run via CUDA and on CPU unchanged. You could not do that with only wgpu...there is no rust shader input, (and the thing that enables it rust-gpu which is used here) and if you wrote your code in a shader lang it wouldn't run on the CPU (as they are made for GPU only) or via CUDA.