That’s close to how I think about it, yeah, but I’d push more in terms of the investment. Since Jekyll, Hugo, Svelte, Eleventy, and the rest just generate flat HTML to upload, there’s nothing wrong with using it for a single page. But you end up needing to learn the whole build-and-deploy process and all the layout quirks, which (especially if you’re starting from scratch) will take longer to get the page out. And like you point out, the more material you have, the better that investment looks.

But then, if you already know the system, there’s no new investment, so it becomes more of a toss-up whether to build things that way, since a page of Markdown is slightly faster to write than the equivalent HTML.