4k is a technical spec. It's the same as lying about the horsepower of your car.
Nintendo (and NVidia) are playing games with specs. And it's incredibly off-putting to me.
Lying about small things means the company will lie about large things. This sort of thing erodes trust, especially because 4k is so easy to test and figure out.
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There are other words for better than 1080p. Such as 1440p or 2k. Which is closer to what the new Metroid game actually does.