The full patch also includes this:

  +Some teams strongly prefer a longer line length. For code maintained
  +exclusively or primarily by a team that can reach agreement on this
  +issue, it is okay to increase the line nominal line length from 80 to
  +100 characters (effectively increasing the maximum length to 99
  +characters), provided that comments and docstrings are still wrapped
  +at 72 characters.
  +
  +The Python standard library is conservative and requires limiting
  +lines to 79 characters (and docstrings/comments to 72).
  +

https://codereview.appspot.com/12269044/patch/1/1001

Good point, didn't see that. It's interesting how clearly it differentiates between core CPython style and 3rd party style. I'm guilty of thinking of PEP8 as the definitive general style guide. But this not what it claims to be- it's just the core development style guide. So it's reasonable for it to be a bit conservative while saying, this is a hardline stand that you may want to deviate from.