Looking at the following page of Tomcat 10.0.0-M8, http://tomcat.apache.org/tomcat-10.0-doc/config/index.html it says "Apache Tomcat 9 Configuration Reference". That string is configured in webapps/docs/config/project.xml Looking at the history of that file and r1637337, the version is also mentioned in the following file: webapps/docs/architecture/project.xml http://tomcat.apache.org/tomcat-10.0-doc/architecture/index.html
Fixed in 10.0.0-M9 onwards
I manually patched the published documents, in a hope that search crawlers would notice the change earlier. (People may be using "Tomcat 10" or "Tomcat 9" as a search term to limit their search to a specific version.) - r1882138