Ben's right regarding the facts. Here's my examples.

Python 3.6.9 (default, Jul 17 2020, 12:50:27)
>>> def foo(*argv, **kwargs): return argv, kwargs
>>> foo(*'ab', x=1, y=2, *'cd', z=3)
(('a', 'b', 'c', 'd'), {'x': 1, 'y': 2, 'z': 3})

Python 2.7.17 (default, Jul 20 2020, 15:37:01)
>>> def foo(*argv, **kwargs): return argv, kwargs
>>> foo(*'ab', x=1, y=2, *'cd', z=3)
SyntaxError: invalid syntax

Also, in Python 3.6.9

>>> foo(**{}, *())

is a SyntaxError, but

>>> foo(x=1, *())

is not.

I think the change happened as a result of

PEP 448 -- Additional Unpacking Generalizations

https://www.python.org/dev/peps/pep-0448/

It reads, in part,

Function calls may accept an unbounded number of * and ** unpackings. There will be no restriction of the order of positional arguments with relation to * unpackings nor any restriction of the order of keyword arguments with relation to ** unpackings.

Ben also asked: This is against the understanding of unpacking, is this intentional?

I was surprised at the unpacking behaviour. My first thought was that Ben had made some mistake regarding the facts. So I made the check you see above.

Jonathan