You can project VR content on to a flat screen. You don't want to look at it that way, but you can do it. The part that makes it 3D is entirely down to the lenses and optics used. The display inside is just like any other.
That’s an extremely pedantic interpretation of the word video. The game isn’t designed to be playable on a screen with regular control input. It’s a video game the same way a full flight simulator is. Technically true, but it requires specialised and expensive hardware to “play”.
Hardly specialized and expensive, it works fine with a $300 headset aimed largely at serving as Facebook's next social platform hooked up to your PC. It's like saying a Wii game isn't a video game, or that games you can't play without stereo headphones aren't video games.
Because it is video.