Understood. I think this is one thing that confuses everyone until they figure out how GrapheneOS does it, including myself. OS and app releases go through a few stages before they're in the stable channel. I think release announcements are when apps/OS releases are in alpha.
And something I forgot to mention. I think the new Apps release uses APIs added in the newest OS release, so if you're going to change to beta for Apps, you might want to change to beta for your OS channel too.