"Other questions, are the demo and full game data separated?"
This may be the best theory so far. I wouldn't attribute anything to "bots", we're still talking about a fairly small amount of downloads overall, and there's zero motivation to bot any of this. Just statistically odd. But there is indeed no differentiation in the analytics between the main game and the "demo" (ie the Japanese patch). So it certainly could have been that a bunch of Japanese people pirated the game and then decided to grab the translation, though again, odd that it would all happen on the same day.