Well, I suppose it is true they'd prefer something of their own design than something we slap together that functions as if it were one, but unless the Malnosso happen to give us either a bucket full of working Poké Balls or someone from their world over the age of 13, I'm just saying that they might not have a choice.

Besides, if Ash is honest when he says that someone from his world could make Poké Balls out of a piece of fruit, [Dear spirits, why are you even repeating this story Sokka? He's shaking his head even as he says it,] anything that we manage to slap together probably couldn't be too bad?

Though we probably wouldn't want to experiment on one of theirs, you're probably right.