Thanks all. This is helpful, if only to confirm that I'm not missing anything obvious =)
Maybe to narrow down the discussion, I did find the Type-specific distance functions, where I'm running into a hurdle (on Apple platforms) is that generic functions over any SIMD type aren't able to figure out which of those functions to call, and so I'm essentially left re-implementing them in a general case.
Maybe this isn't a common issue, but I did note this thread in which I think @scanon was essentially saying this was a TBD feature. Is that still the case?
Thanks for your help so far!