> ...distinct but able to interbreed

I mean people won't like the idea but that's not my point; what you describe variety in superficial traits while maintaining common traits

Applied to humans; skin color, eyes, dwarfism, hypertrichosis... can still interbreed

When it comes to categorization and taxonomy in leaky abstractions like languages the boundaries get a bit hand wavy and usually land on whatever fits the prevailing social desirability bias of the day