I had downloaded it but never rebooted to update because I heard about some issues and decided to wait. Now it's saying I'm up to date with Android 13?
It's not impossible. The update isn't set in stone until you reboot into the Android UI. Prior to reboot it can be discarded trivially. Post reboot but prior to starting up the Android UI, it can be rolled back.
It would be interesting to see if it's an actual cloud-controlled recall feature or whether it's something simpler like timed expiry of an installed but not activated update. Haven't dug into update_engine for that. Could also be in the upper updater layer, outside of update_engine.
At least on Chrome OS, update engine does have a recall feature. The server can say, "if you've downloaded and installed an update and you're waiting to boot into it, cancel it and stick with what you have"