Grammar and style looks pretty much fine. Mainly the refcounts.dat file needs to be updated.

I will say that in the example of the four functions, I would probably group the "explanation of the function" parts a bit differently, because the explanation of the syntax is separated from the demonstration of the syntax, which means you have to either remember it perfectly or scroll up.

I'd rather see something like:

"A standard function definition does not restrict how arguments are passed, so they can be passed either by position or keyword:

>>> def standard_arg(arg):
 ...        print(arg)
>>> standard_arg(2)
2
>>> standard_arg(arg=2)
2

If an argument is specified to be positional only, it is an error to pass it by keyword:

>>> def pos_only_arg(arg, /):
...        print(arg)
>>> pos_only_arg(2)
2
>>> pos_only_arg(arg=2)
Traceback (most recent call last):
...

"

I understand that it's a trade-off, though. In your version, the contrast between the different syntaxes is highlighted, since all the definitions are right next to each other, whereas in my version the syntax is kept close to the explanation.

Looking great, some small optional nitpicks though I am not a native speaker :).

A few minor corrections/comments. Thanks @pablogsal 👍