Nice interview, @PaulAlcorn . I like how you hammered on memory bottlenecks - that would be my concern about running a 64-core threadripper.
If Hallock's statements are taken at face value, then I'd guess where Epyc's 8-channels really come into play are:
Dual-CPU setups, where you could actually have more than 64 cores beating on a single CPU's memory.
Servers with high I/O load - such as from NVMe drives, high-density networking setups, or even GPU/AI accelerators. These devices all tend to work mainly to/from buffers in RAM.
Still, I'm skeptical that a great number of workloads wouldn't scale better to 64 cores, with 8-channel memory. I look forward to Threadripper memory overclocking benchmarks hopefully shedding more light onto this situation.
Where I think a 48-core Threadripper could make sense is specifically for workloads that do hit bottlenecks at 64-cores. In those cases, 48 cores should offer a bit more performance than 32, but would be more cost-effective and perhaps also more power-efficient.