This part never made any sense to me. Such an easy fix to make.
This rule would mean contributors would actually care to initiate a conversation about their intented work, and would probably drive them towards projects where there is some activity and positive feedback from the maintainer, instead of projects which didn't want or ask for any contribution, like it happens now.
Also, I think such constructive environment could drive a reasonable maintainer to help the contributors by fast-tracking the PR in case the end of October was approaching. And by taking into account the PR merge date, not the PR creation date, it would mean you as participant could start working on some PR even before October.
Now when I get a PR, I treat it as patch and merge it locally, before syncing the mirrors.
But then it is shown as not merged on Github. Especially the verified by github hash is cannot be stored in Mercurial
Regardless, IMHO if someone wants to do a PR on your repo, asking you should be their first step.
Less shirts going out == less shirts being worn == less DO's name plastered on every programmers' bodies.
This is not to say that Hacktoberfest hasn't been helpful for some Open Source projects but let's not pretend that DO's main goal isn't marketing.
(BTW, there is nothing wrong with that, they are a company who wants to earn money, and this way, they help Open Source a little bit too)