The DuckDuckGo addition hasn't landed in Nightly yet. It has rolled out to the release channel, and should be in all channels shortly.

It just rolled out in the stable 33.1 release today. It will hit the other channels (Beta, Aurora/Developer, Nightly) shortly.

I get that this isn't a code change and so this probably isn't critical, but, still, isn't that exactly backwards?

Yup. To time the release with the tenth anniversary, it had to go around some of the normal release engineering and localization processes.