>>34500172Not OP, but I think they meant Apricorn Balls there - "you could still go back to HGSS to get more Apricorn Balls before they were made available again in Sun and Moon." By contrast, Dream Balls can only be used to catch Pokémon in the Entree Forest, and the only Pokémon there are ones you transfer from the Dream World, which is closed.
You can still use the Dream Radar to get a very limited supply of Pokémon, but nearly every Pokémon from the first four Generations was available in the Dream World, so that leaves a ton of Pokémon that are legal in Dream Balls but can no longer be caught in them, only passed down by breeding.