Why are Pokemon like Spiky Eared Pichu not usable in National Dex?

Question

So as you may or may not know, Gen 8 National Dex is a Metagame exclusive to Gen 8, that brings back Mega Evolution, Z-Moves, and Pokemon that were in past gens that are unobtainable in Gen 8, such as Greninja and Banette

So my question for you is, why aren't Pokemon like Spiky Eared Pichu and Cosplay Pikachu allowed in [Gen 8] National Dex?

Answer 1

All Pokemon that were legal at the end of the 7th Generation are legal again. This does not include never released Pokemon like Floette-E. This also does not apply to unreleased Pokemon in Generation 8, such as Gigantamax Melmetal and Zarude. Finally, this does not apply to Pokemon that were legal in a prior game but not in Generation 7, such as Pich-Spiky-eared and the Cosplay Pikachu formes.

Source

Comments

Dang, would that mean this also goes for other National Dex like metagames, such as Metronome Battle?

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That I can't say. I've never even heard about something called metronome cup

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Oh whoops. I meant to say metronome battles

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Haven't heard of that either tbh

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@JustATypicalPerson No lol. You can get anything in Metronome Battles, even the CAP and other hackable Pokémon, bar a few versions of PokéStar, like Spirit.

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Really? I remember trying to use her on that metagame, but not being able to do so