I'm completely unsure as to what scanlines even refers to, but what I do want to say is that a lot of the older systems (NES and Genesis, mainly) too advantage of "pixel bleeding," or "color bleeding," meaning they could display more colors because the things you saw on screen weren't very sharply defined. The colors from one pixel would bleed into the one next to it and this would create (in the eyes of the player) a new color. Yes game designers did this on purpose. Which is why sharpening up the graphics on these old machines (either thru HD, RGB modding or the VC stuff) makes certain games look worse than they use to.