The process to add meta tags to Portal pages could use some clarification. Reading the documentation Adding HTML meta tags for Search Engine Optimization, one might expect that an author could update the page title or add meta tags or do both. That does not seem to be the case.
If you find meta tags not being added to your page markup, make sure you override both the page and portlet title. This process is described in the first step of the documentation. In my screenshot, I’ve set it to an WCM element, but you could set it based on WCM content. Just make sure to set both!
Documentation will be updated. A relevant section of existing doc is, “Web content viewers that are configured to override the HTML title can also add HTML meta tags as portlet preferences.”