>>37499718First off, neither Nintendo nor GameFreak really need to say anything about it because nothing about this leak affects their bottom line.
As for the authenticity, we have video footage of Spaceworld that confirms the sprites and color palettes. We've had people who regularly deal with data like this, including previous fake "leaks", that have confirmed its authenticity. We have enough evidence to suggest it's authentic, so unless new evidence comes out that suggests otherwise, we just have to trust that it's the real deal.