I'm not sure that's true anymore. 4k resolution means that you can now fit two 4:3 monitor's worth of pixels (1920x1440) width-wise side by side on a single 4k

I'm not sure that's true anymore. 4k resolution means that you can now fit two 4:3 monitor's worth of pixels (1920x1440) width-wise side by side on a single 4k (3840x2160), 16:9 screen. It's almost 2 monitors in one.