Well, you could consider any game's hook or premise would be non-spoiler info while specifics would be spoilers. For instance, FLUDD in SMSunshine as part of the whole premise of the game isn't a spoiler. In Galaxy, the central concept is the planet thing, but knowing about Mario's new power ups (bee suit, ghost mushroom, etc) are added bonuses one would be surprised to see.
This is one of those areas where games and movies share some stuff in common. Movie trailers have to sell you on the movie without giving away too much of the plot. Here, the plot is a spoiler, but in some movies plot is all there is. Studios have to give you some without giving away all of it.
The line may be a bit fuzzy in both areas, but I think it's safe to say that this was kinda spoilery.