Further quote: "This will often be useful for writing minilanguages, (for example, in run control files for Python applications) or for parsing quoted strings."

Why shouldn't that feature not be available under Windows?
Again, shlex is *not supposed* to handle Windows command lines.

Also, http://docs.python.org/lib/shlex-parsing-rules.html clearly says what the difference between
"posix=True" and "posix=False" is.

That non-posix mode works on Windows filenames is because it does not handle backslash escapes.