Canonical have done most of the work for LXD (including directly employing the main developer for years). Until now, they've been doing it under an umbrella project that was specifically not Ubuntu focused (to quote linuxcontainers.org: "The goal is to offer a distro and vendor neutral environment").
Now they've moved the project directly under Ubuntu, why?
The answer to me seems to be that they still going to do development, but they will no longer try to support anything but Ubuntu (and really, my guess is it will go the route of microk8s and become snap only/first, so more of a middle ground).
And I don't really blame them for that - they're doing the work, they can focus on themselves. But it does mean there is now a need for someone to do the work to become the packager for other distros. That development has to happen somewhere else now.
That may well be this repo, it might not.