The documentation page https://docs.python.org/3/library/tkinter.html states "Passing the config() method the name of a shorthand option will return a 2-tuple, not 5-tuple."  While config() without argument does return a map that yields references like this, if config() is given the shorthand name as an argument, it follows the reference to the long option name and does yield the full 5-tuple.

To demonstrate the difference:

from tkinter import Tk

Tk().config()['bg']

Tk().config('bg')