|Let's look up Wikipedia article "Static web page"|
> A static web page (sometimes called a flat page or a stationary page) is a web page that is delivered to the user's web browser exactly as stored, in contrast to dynamic web pages which are generated by a web application.
what Next.js and Gatsby actually do is they statically source your content and generate a dynamic React App
the generated React App then adds dynamic functionality, for example if you navigate the page instead of redirecting you to the page itself, it will redirect to a virtual route
once you hit the virtual route, Gatsby for example will fetch a .json file with the page contents and render it dynamically via React
if your aim is to create a truly static site, you should use a real static site generator, examples: Hugo, Zola and Jekyll
stop calling Next.js and Gatsby static site generators! They are not, they are React App generators with statically sourced (bundled) content