Where scripts includes anything you can compile to wasm. That enables a lot of interesting stuff. Including, say, compiling some lisp to wasm to e.g. retrofit some emacs stuff via a vs code extension. Probably a bit redundant but it would not surprise me to see some code sharing long term between the two ecosystems via wasm.
As far as I understand, VSCode extensions do not have the level of unfiltered low level access to the internals of the editor. In emacs there isn't really a difference between extensions and core features. It is just all code running in a lisp vm (and it is also the reason I'm sceptical about having other extension languages in emacs).