Angle is ultimately a OpenGL|ES implementation on top of other APIs since webgl is pretty close to GLES, but desktops don't typically implement GLES.
This (IGL) is more a layer sitting on top between your app and the system provides API since pretty much every system has a different blessed API these days: Browser:WebGL/WebGPU, Windows:DirectX/Vulkan, Mac:Metal, Linux/Android:Vulkan, Consoles: Proprietary APIs like NVN/GNM/AGC/DX12 with a lot of extensions.
Just about every major cross platform 3D graphics app/engine has a layer like IGL, this just seems to be an attempt to make Meta's a standard.
Technically there's also a driver layer sitting between the DirectX 'client-side' API and the hardware, so it's even worse ;)
(the whole point of more modern 3D APIs, which move most of the expensive "abstraction-layer translation work" into the initialization phase is to "cut through" all those layers in the frame loop though)
This (IGL) is more a layer sitting on top between your app and the system provides API since pretty much every system has a different blessed API these days: Browser:WebGL/WebGPU, Windows:DirectX/Vulkan, Mac:Metal, Linux/Android:Vulkan, Consoles: Proprietary APIs like NVN/GNM/AGC/DX12 with a lot of extensions.
Just about every major cross platform 3D graphics app/engine has a layer like IGL, this just seems to be an attempt to make Meta's a standard.