You'll have to show me what you mean about "This game has not been reviewed by Nintendo Power staff. I stopped subscribing at issue 131 so I missed a lot. It could be that they're acknowledging that they have not taken the time to rate a game with a score yet, but they currently have coverage of the game so they are going to show that (in other words, they've written out a small guide to Ocarina of Time, but they just have review the game for a score). 

If your comparing Nintendo Power magazine to internet sources than that's an entirely different thing. A magazine, any game magazine, is going to be a month behind what happens on the internet, because the internet instant. It takes a month just to get a magazine done. 

And everytime Nintendo Power reviews a game (as in the strategy section with maps and tips), they only go so far, especially when it's their own games. Its just enough coverage to get you far enough in the game, but they will always say "Look for the official guide from Nintendo" at the end of their review. They review the game enough for the magazine, but for the entire walkthrough of the game, you need to buy the guide. For example, they only reviewed so much of Super Smash Bros. Melee, but if you want to know everything, you buy the guide. As each month passed in NP, they did more coverage of Smash Bros. in the Classified Information section, revealing how to get the hidden characters and in another month, trophies and stages. It's also similar to a manual and whatever help it comes with...it gets you so far into the game, but if you really need help you get the guide. Nintendo Power goes further than a manual. 

I've been subscribing to Nintendo Power since issue #22 and reading it before then, and up to issue #131 and buying it from time to time afterwards. From my experience, Nintendo Power has always had early coverage of games. Perhaps sometimes they just haven't gotten around to actually rating a game that month, but can have coverage of it. Or maybe they fall behind and don't have room for a game this month. Illusion of Gaia was suppose to be reviewed in the next issue, and even had a picture of it in the table of contents, but something came up and Mortal Kombat II was reviewed instead. Illusion of Gaia got coverage next month. Sometimes NP will have coverage a month or so before the game comes out. The A Link to the Past review was done before the game was out in stores. It even said on the first page of the review something like "Look for Zelda:ALttP in stores on May 1st". You should also know that all games released for Nintendo systems must be approved by Nintendo of America to ensure a certain level of quality (this is also true of Sony). I can imagine a game company sending a game in for approval and it gives NP time to look at it. Then again I'm sure its usually just when a company wants NP to take a look at their game. I know back in the NES days, if you didn't get your game covered in Nintendo Power, it didn't sell.