The support of subgroup-size-control on Metal is still under discussion.

• Metal doesn't support specifying the SIMD group size in a compute shader.
• According to Metal document, "don't assume the size of the SIMD groups".
• In many open-source projects (dawn ) the GPU SIMD group size on Apple silicon are assumed to be 32.
• subgroup-size-control cannot be supported on Metal using non-Apple silicon GPUs.