You could buy a 64 processor machine in 1990, but it wouldn’t have been a 64 core machine in the sense we’re talking about — a single socket system. This isn’t some trivial distinction either, as the whole memory architecture is very different indeed for the two scenarios.

Even in single-socket configurations, Threadripper and EPYC are still both NUMA architectures - the cores are split across two or four dies, each of which has its own memory controller and memory attached to it, with requests from a core to memory on another die going via an interconnect.