There’s an important difference here. The 1K mode is using the CGA adapter’s composite NTSC output to a standard (American) television set. It’s taking advantag

There’s an important difference here. The 1K mode is using the CGA adapter’s composite NTSC output to a standard (American) television set. It’s taking advantage of color television’s design to effectively turn high-frequency pixel value changes into new colors. The original article discusses the sixteen colors supported by the digital monitor that IBM sold for CGA cards. It’s very different from a television set because the monitor itself converts the CGA’s 4-bit digital signal to CRT control. This monitor is completely unable to display the 1K color hack because, even though it’s also CGA, it’s not an NTSC monitor. The upside of such a digital monitor was much better picture quality. CGA’s 80*25 text mode was practically unreadable via composite on a TV set, you needed a proper monitor. (They were also expensive. An IBM color monitor cost several thousand dollars, probably like $10k in inflation-adjusted 2023 money.)