Doesn't need it, the CPU is only 350W TDP for the 96 core variant, but a rig like that tends to also be loaded with 2-4 GPUs for compute workloads and a fuckton of ECC memory, which tends to use (far) more power than standard dimms.

I'm installing a (1+1 redundant) 1200W PSU for now, as I initially will only have a single GPU and a single DIMM per memory channel to do the platform validation.

In your typical gaming setup, you could perfectly use a single PSU, even an 850W one would probably do just fine as there's no games that'll 100% all the cores anyway and threadripper cores are ludicrously well optimized for power, especially compared to anything Intel offers in the desktop, workstation or server market.