>>29596975I would argue that they are, functionally speaking, more valid as separate species than things like Illumise/Volbeat and Plusle/Minun.
Alolan Vulpix, for example, has a different type, different movepool, possibly (but not definitely) a different stat distribution, a different evolution method; if they had just changed its name, it would be far more distinct from Vulpix than the examples I listed above.