I think the goal here is for the semantics to basically be SPIR-V, and for people using SPIR-V toolchains to be able to expect WebGPU platforms with a Vulkan backend to execute basically the same SPIR-V after the conversions to/from text.

Knowing Vulkan, WebGL, and OpenGL and working a bit with some of those technologies while hobbying the others, WebGPU will take about a decade to be fully adopted, and even then, only by a fraction of companies that are willing to spend manpower resources into developing something interfacing low level graphics directly.

WebGPU is important for game engines, currently it is missing a lot of features so you can't write the shaders you want.

I agree. Originally SPIR (without a V) was just a 1:1 copy of LLVM IR with no commitment to backwards compatibility. Every time LLVM IR changed SPIR had to change as well. This lead to two major versions of SPIR. Clearly this is not a sustainable solution. Implementing several versions of the same IR is a huge support burden for almost no benefit. Now we have the successor SPIR-V which is no longer tied to LLVM IR. Anyone can implement SPIR-V support without LLVM. There is no excuse to not use it. It's basically the same story with WebAssembly. LLVM IR wasn't good enough so someone had to actually do it properly this time.

That's because there is no rational reason. The reason this is at it all an issue is because Apple put their foot down and flat out refused to implement SPIR-V.

They also refused to implement WebP support. If they can't get their act together I'll still get my revenge by using a polyfill that decodes WebP images with Javascript (goodbye battery life!).

I dont want an Google Image format so I am glad they dont support WebP. I much rather they support JPEG XL.

The willingness of the various web consortiums to bend over backwards for individual corporations has got to end. It's making the web worse, not better.