The shared use of Markdown is probably what creates the relationship between static sites and notebook apps. Unfortunately, both categories tend to extend Markdown in different ways: Notebook apps with things like [[wikilinks]], and SSGs with (IMHO, unnecessarily) opinionated approaches to linking other files.

You can make notebook apps play nice with SSGs (see, for example, my websites), but it takes a fair amount of up-front work and planning + you loose some of the affordances of both.

There seems to be a bit of cross-over in the Obsidian & Jekyll communities though. Something useful/unified may yet come out of that.

Searchcaster