That's interesting, but it's not pixel art.
Pixel art has it's name because you work at the pixel level. You place individual pixels.
It's not an art movement, it simple exists because computer games used to have very low resolution, and small color palettes. You can't rely on scanning things in because you need to draw things so small and with such limited colors that a scanned picture would look very bad, and only a human could figure out clever ways to use the pixels to make recognizeable things. So people had to do it by hand...and that's where pixel art comes from.
You can still find people doing pixel art who work on games that have low res graphics, using limited color palettes.
Techniques like dithering must be used to give the appearance of more colors.
Examples