As I recall it, in the python2 docs we used the [... notation, sometimes even when the actual arguments were or accepted keywords.  In the python3 docs we converted to always using keyword notation...and then realized that that also caused confusion, in the other direction.  Some things we converted back to [... notation.  Then argument clinic came along, and we kind of postponed worrying about it until we converted as much as practical to argument clinic.

I think we are moving toward using (and documenting in the main docs) the / notation.  Especially since it shows up in the inspect module as well as the docstring help.

Martin, if you don't think you have consensus on your patch, perhaps it is time to ping python-dev.