Hi Isarra,
Why is this ahead of schedule? Two months before release seems pretty reasonable to me; You don't want to rush this stuff, especially when balancing with breaking changes in the next release.
It's ahead of the planned release schedule [1] by a few weeks. The real issues is, though, that the branching was not announced a week beforehand, as planned. As you point out, the whole tarball release of a major version should not be done in a rush. This also implies giving developers, especially when it comes to extensions, some time ahead to include their work (in progress) into the branch without a lot of backporting.
Also, 1.24 has already had wmf22 branched. Shouldn't this mean master should be going onto 1.25 now anyway?
IMHO, the issue is that we have no clear responsibilities here. The Foundation sets the date for switching to wmf1.2x+1. Probably this should this be the trigger for the 6 week tarball release process. On the other hand, we have a monthly tarball release cycle and announced dates for releases which a lot of non-WMF users refer to. So we need to coordinate this. Mind you, I do not want to totally stick to the 6 week process we have lined out, there is of course flexibility. But it needs some coordination before the branching is acually made. I assume it is within the responsibilities of WikiReleaseTeam to make sure this coordination takes place (in the future). Personally, I also think the WikiReleaseTeam should do the acutal branching and communication about this.
Let me be clear about one thing: this is a matter of unclear responsibilites. I'm not blaming anyone personally for what they did. Let's clarify the process (maybe here on this list) and make _better_ mistakes tomorrow :)
Best, Marks
[1] https://www.mediawiki.org/wiki/WikiReleaseTeam/Release_timeline