No, Gamefreak did not (who are they?

). The game was developed by Game Freak (Inc.). Considering that Nintendo funded the title, localised it, and published it, stating that Nintendo made the game is not inaccurate either.
And it's pretty clear what I was looking at. If we are just looking at Nintendo's internally developed music titles, what do we have apart from the Rhythm Paradise series and Jam with the Band? If we look at Nintendo-published music titles, we also have Sound Voyager, Donkey Konga, Elite Beat Agents, and Sing Party.
Sometimes just use your brain and shut up
By the way, you can also buy coupons for games that you already own. Since I did not know what to do with my platinum coins, I bought the Hydroventure coupon (I already bought the game before) to see what would happen. The reduced price even shows up on the respective 3DS eShop page.