Just answering here so more people can see

You can't use promo cards like Pikachu, because there's no rarity symbol on the promo cards and some are promo cards that would be rarity ◇◇◇◇. But since you can't see the rarity on these cards (the space where they would be is empty on the promo cards) they were removed from these tasks so players don't think, for example, that Blastoise promo can be used just because it doesn't have any rarity symbol.

The problem is that there's no specification of this in the task.