Your own link stated that Microsoft hacked."Processor groups" is not a hack - it's an elegant solution to the problem of how to schedule large numbers of cores that are bigger than the largest integer mask supported by a processor.
Links? With supporting evidence that processor groups is the problem?
Example that I find now:
Hey everyone. Running Windows 10 Pro Dual LGA 2011 mobo Dual Xeon E5-2696 with 18 cores each (2.2 GHz) So... in Windows 64-bit, it can support up to 256 cores BUT... If you have over 64-cores, it breaks them up into even groups for processing. For example, I have a dual xeon setup, each xeon...
AMD's official line is that there's no 48-core Threadripper because most people buy the top or the "sweet spot" part.