Analog = 'sine waves', not 'square waves'. So if you have the left side of the screen white and the right half black then there will be a point in the middle where the signal, no matter how the PAL or NTSC is encoded on a carrier wave, has to do 180 degree change. So this affects the signal and the 'aliasing'. It isn't a mismatch of dots in the horizontal only approximating defined rgb columns, it is all in the 'sine waves'.