The continually updated docs are built from the stable branches, whose version remains at (e.g.) 2.7.2 until 2.7.3a1 is released, at which point the continuous updating stops until 2.7.3 is final.

I don't think presenting docs with an alpha version on the http://docs.python.org/ frontpage is useful. On the other hand, I do think it is important to have doc fixed reflected (more or less) instantly somewhere, so that e.g. people reporting typos can see the fixes. The status quo is a compromise between these two needs.

When we do make backwards incompatible changes or additions during a stable cycle, they need to be marked with "new/changed in version 2.7.X+1" anyway.  So the SequenceMatcher change would alert users itself. If not, that's a bug.

About the "obsolete" snapshots: I don't know what you're referring to there: if it's the released docs for specific versions, then I think that's standard practice to have a doc version released for a specific Python version; and I wouldn't change that.