I think 'rendering' here means something like 'doing what's needed to produce the final HTML for the browser to render'. You can produce the final HTML on the server (server side rendering), or the front-end (e.g., via DOM manipulation), or mix them up (e.g., HTMX replacing parts of the DOM with pre-rendered HTML from the server).

i.e., there's two different steps that each do something that can be called 'rendering': templates to HTML, and HTML to what the user sees in their browser.

I'm inclined to agree with the main sentiment of your post though, and lean myself towards solutions that rely on the server heavily with just a splash of javascript on the front end.