Chrome dropped support for Yosemite a while ago, so my guess is that the old version of Chrome running on your Yosemite machine is only “aware” of the availability of the High Sierra update.
I’ve also noticed that some of the Chrome support documentation is running behind the actual software and still says that 10.13 is required for updates.
I have one Mojave machine still running, and Chrome, Brave, etc have been warning about the need to upgrade to Catalina to continue receiving browser updates.