Yeah, I was kinda thinking the same thing, like it seemed unlikely for them to do this, releasing an old, long passed forgotten, unreleased game.
Especially considering how they are thorough with quality, and this one never passed their quality control standards before.
But it's an interesting way to attract attention to this product. Unexpected. Not that it needed it though. It's gonna sell out worldwide in 0.1 seconds.
Actually it was in quality control according to Wikipedia, that base it on statements of developer Dylan Cuthbert:
"In an interview with Nintendo Life in 2015, Cuthbert reveals he has a copy of the game's finalized ROM image, completely reviewed and debugged by Mario Club, which he acquired during the development of Star Fox Command, and states that the mastered ROM image sustains many elements that remain missing from the leaked prototype ROM images."
Hmm, we might not have seen this earlier, because:
"In a 2015 interview, programmer Dylan Cuthbert revealed that releasing the game on the newer Nintendo eShop is also very unlikely due to major legal disputes between Nintendo and Argonaut Software, despite the fact the latter is defunct."