The current WebGPU spec is basically the common feature subset across desktop and mobile GPUs, and what of those hardware features are actually exposed by D3D12

The current WebGPU spec is basically the common feature subset across desktop and mobile GPUs, and what of those hardware features are actually exposed by D3D12, Metal and Vulkan. If something is missing then it's most likely the fault of some random mobile GPU. Such missing features might be added later via optional extensions, but the focus was to get the thing out of the door first.