I'll speculate. It's been since September since newer features of V13 were last updated in the release notes. The fact that we not only haven't seen these updates (3x this and that), we haven't even heard a whisper about them. I think we have a combination of issues.
First, the team has been focused on other FSD promises since September, including foreign country releases, and then robotaxis. There must be a ton of enforced learning there that will have to benefit the rest of us when we get it.
Second, that last part of V13 sounds like it was tougher than expected - save the hardest parts for last. I think parking lots alone and parking in general is probably a lot harder that driving on the highway. This part doesn't really stress the vision system or need speedy reflexes. It needs a competent planner, which it obviously lacks in 13.2.8. I still don't know how they do neural net training on a particular task (like mastering parking lots), but perhaps their initial plan didn't get the results needed.
That said, what's next for us? I think v13.3 - or jump to v14.x. If the robotaxi work pays off, perhaps jump right to it.