I actually agree, since it looked to good to be true to be gameplay. (I myself would get confused if the gameplay actually was like that). But again, many claimed that the footage seen was actual gameplay (when I didn't even believe it was 
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Nah, it's like I said (and like the link you posted seems to confirm), this was in-engine, but probably not rendered on an actual Wii U-console. This is like I said common practice, and it's not really something they do to 'trick' the consumer, as much as it is to ensure high quality screenshots for stuff like print magazines and websites. One could argue that upping stuff like the resolution is misleading when it comes to representing the actual, finished product, but everybody does it and it's become so normal that the assumption is that people are aware, and simply prefer the higher quality screenshots.
I think it's going a bit far when you start adding effects that won't actually be rendered in the final game, but at the same time you never really know about all the things you as a developer need to cut in order to ensure the player gets a smooth gaming experience. Because testing often happens on debug consoles and computers, which mimics the hardware of a Wii U, though they almost always come with extra juice. This is because, especially the debug consoles, are also running a lot of other stuff in the background, compared to a normal Wii U console that focuses most of its power on running the game.
The only reason I know this is because I've had to use debug consoles for work. Sometimes publishers send us press copies of games that will only run on a debug. This is to reduce the risk of leaks before launch, usually.
Don't get me wrong though, this is still a very good indication of what the next Zelda game is going to look like, because they must be pretty far into development at this point. I'd imagine it'll look nearly identical, give or take some particle and ambient effects, and possibly a shorter rendering and draw distance.
(Damn it).
