I awoke this morning to an email from the LiveJournal Community Care Team explaining that the changelog is beta code and that they would have fixed this before release:
Given hope, I went and checked out the changelog. True to their word, r16042 rolls back the commits associated with the gender field over the last few days.
Hopefully when this comes back it will retain an "Unspecified" field and add "Other".
Given that the first diff went in on 2009-12-10, I kind of wonder how long it would have taken before somebody inside LiveJournal had caught this and fixed it [and how they would have fixed it] had synecdochic not caught it and pointed it out.