It is still in beta, and has been in this state for a long time. At some point, the developer thought to delay it further and introduce whatever breaking changes are needed in this release.

Note that if you use, say, the 2.11 version, you cannot upgrade to 2.12, you cannot go back to 1.X either. People like me were stuck, it turned out you have to discard the repo. Sometime later they better clarified this point:

>> Borg2 is currently in beta testing and might get major and/or breaking changes between beta releases (and there is no beta to next-beta upgrade code, so you will have to delete and re-create repos).

I have a 2.X repo. It’s working fine and backs up. I have a lot of snapshots in that repo. If someone knows how to transfer them to a 2.X version once it’s out of beta, let me know.

Author calls that out right at the top of the changelog:

> Beta releases are only for testing on NEW repos - do not use for production.

That's fair. There's a lot of software that is generally ok to use in beta, however, and this has been in beta for a long time.

Beta is beta. Hard to fault the developer using this label correctly with a clear notice for the way some other projects treat 'beta'.