The blog doesn't link to that support page because that support page isn't related to this. It's out of date and was written when MacOS originally dropped support for 32-bit apps starting with Catalina. Valve was letting people know that even though they wouldn't be able to play their 32-bit games if they update to Catalina, they would still be in their library and available to install on Mojave and earlier. Valve was still supporting the 32-bit Steam client back then.