On 22May2018 0741, Guido van Rossum wrote:
ISTR there are plenty of PEPs that never get posted to python-ideas because they are discussed on a separate list.
There are often better venues for the initial discussion (such as security-sig, distutils-sig or datetime-sig), but I think that's orthogonal from posting the full text of a PEP.
That said, if the aim is to keep discussion in another place (such as github), you really don't want copies floating around any other mailing lists. Eventually I'd hope it comes through for final review though, as I'm sure a number of us are unlikely to click through to github unless we have a specific interest in the topic.