It is a WIP web standard. And the spec is still evolving most things are stable at that points, but new features are still being added, like this one!).
And that's how the web works, it was the same for WebRTC which spent 2-3 years in such a state, same for MSE, etc.
WebGPU is brand new, and the paint is still wet. It doesn't make sense to dismiss things that haven't landed in browsers yet as “unusable on the web”.