> The table headings 'Standard installation location' (of what?)
Of software projects using distutils.

> and 'Default value' (for what program?)
For a CPython without changes to the default build configuration.

> both seem a bit ambiguous, or rather they seem reversed to me. I
> would label the columns 'Default module directory' and 'Standard
> Python location'.
Well, no: the first column does not contain real paths, but templates with placeholders like prefix and X.Y.  The second column gives the path with the placeholders replaced by their default value.

> That said, I hope that the actual default module installation
> directory for install is the actual site-packages directory on
> my machine, based on where I actually put python,
Yes.

> and not the non-existent standard location, which I did not use
> but which is what the text seems to say (but which would be a
> behavior design bug to me).
“Default” means “if you haven’t made any change to the build/install configuration of Python”.

Do these replies make sense?  If so, I can rephrase them as a doc patch.