Yes, once you make the connection between every single keypress invoking an elisp function, and the various help combinations (variables, functions, keystrokes as you mention), I think Emacs is actually the most "discoverable" editor that I've used.
M-x completions aren't really "fuzzy" out of the box. `partial-completion` is in default `completion-styles`, yes, but then you have to do word breaks with dashes manually.
Except when the name of what you look for doesn't match your mental model (yep, I'm in the group of people who think software should adapt to human and not the other way around)
Example : I want to change the encoding of a file when I load it... Good luck figuring that out without resorting to reading the documentation.
And here I would argue that, since the documentation is included with Emacs and can be pulled up in the editor, this is still a point towards its inherent discoverability.
Again when you load emacs there's a link to the manual on its splash screen and as a guided tour. A lot of people rush to turn off this screen or suppress the menues on startup (which I get, the menu bar is pretty ugly) but they do have useful functionality for someone who doesn't know Emacs.
If I'm not mistaken when you install vanilla Emacs the screen even includes a tutorial and guided tour that both tell you these commands.