To expand further, for everyone.... When ubnt releases a new stable on their forum they provide a direct link that's available immediately. It doesn't make it to the official repos/software page until usually a week or so later, in case a last minute bug is discovered as it limits exposure. This has happened on more than a few occasions over the past couple years which is why LS.io calls the stable path "unstable"
This is why when you see the release notes, this container isn't updated immediately as the software isn't generally available yet. There's another container provided on this forum in which the creator pulls software from the ubnt forum, if you can't shutup and wait, use that one. Those of us that understand the LS.io deployment model are tired of seeing "why aren't you on x.x.x yet!?" every other post.