I was googling public NVIDIA SXM2 materials the other day, and it seemed SXM2/NVLink 2.0 just was a six-way system. NVIDIA SXM had updated to versions 3 and 4 since, and this isn't based on none of those anyway, but maybe there's something we don't know that make six-way reasonable.
It was probably just before running LLMs with tensor parallelism became interesting. There are plenty of other workloads that can be divided by 6 nicely, it's not an end-all thing.
