I remember a leak about convergent evolution, that process where completely unrelated species evolve into basically the same shape. If I remember right the leak said the new Diglett was one of those.
So technically speaking it's not a regional variant, since those are divergent evolution, the same species adapting to different environments. Diglett and Wiglett have different ancestors and both of them adapted to look pretty much the same.
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Functionally though it's just Paldean Diglett