Do keep in mind that RDNA3 WMMA is very slow, running at the same theoretical TFLOPS as shader (which are doubled from RDNA2 due to very limited dual issue support that can be used in WMMA). Nvidia tensor cores and Intel XMX can run closer to 4:1 or 8:1 or so compared to vector workloads.
> It just feels obviously wrong to do wave-8 right of the gate
That's because Alchemist isn't a a true first generation product, it's a scaled-up version of Intel's (relatively mature at this point) integrated graphics product. This means that Alchemist has suffered large growing pains (Gen12 was not really designed to be used in products bigger than maybe 128 EUs, A770 is 512 EUs). It also has some form of separation anxiety, seeing its need for ReBAR. I also recall very early in Alchemist's life (pre-release) some driver optimization that had a huge benefit, which was just the wrong memory region being used, as all memory is the same on an iGPU but not a dGPU.