Why doesn't python use its own argparse library for its associated --hhelp?

(Note: The title cannot have the word 'help' in it, so intentionally misspelled).

The python module has argparse to pass command-line arguments. However, when I look at python itself, and doing:

$ python -h
usage: python [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-b     : issue warnings about str(bytes_instance), str(bytearray_instance)
         and comparing bytes/bytearray with str. (-bb: issue errors)
-B     : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x
...

It seems to be using initconfig.c. Why does it use this and not its own library? Is this for backwards compatibility or why are the cmdline args passed/interpreted there?