Emacs is in essence, a virtual machine: http://www.emacswiki.org/emacs/ByteCodeEngineering. That's why you are able to do so many things with it. The whole text editor GUI is just a frontend the Lisp interpreter. You can think that Python comes with an interpreter that runs in terminal. Emacs comes with an interpreter and a whole GUI frontend for its interpreter, not merely a terminal interpreter with a prompt. That's why you are able to evaluate any Emacs Lisp code ANYWHERE.

If you only use Emacs as a text editor, that's fine for using a subset of it. Just like a casual user uses Linux without never using its underlying tools in the terminal.

> saying that Emacs is only a Lisp interpreter implies that the entirety of the text editor is implemented in Lisp, which is clearly not the case.

With this argument, I guess Python is also not an interpreter because clearly it is not entirely written in Python.