What educated_foo is trying to explain is that the tight association between docstrings and functions facilitates writing/understanding code with such functions.

And it's not limited to the emacs editor as you're trying to imply.

I recently heard a long rant about how inferior the perldebugger is in comparison to a certain Python REPL, where imported methods are not only tab-expanded but also dynamically explained by help of the docstring.

That's only possible because the documentation is part of the introspection.

And nobody said that the higher level documentation shouldn't be done somewhere a big POD block or that deeper information to certain functions couldn't be located there.