As far as I understood its worse, as they dont use OSTree but BTRFS snapshots. So they have an image, do atomic updates from some repository (not sure how thats done) and then build the next image. This process is atomic as a fail will cancel the update.
But the fetching or things is done via a normal package manager, its just building differently on your machine, again, aa far as I understood.
Then you have BTRFS snapshots which you reboot into. You can also layer packages, not sure how that is done and if its reversible.