I haven’t reverted, but for every other version of iOS I’ve ever used, reverting requires a full wipe and then a restore from an old backup that was made with the old OS.
Are you saying that you reverted from 26 and downloaded and installed iOS 18 from the cloud?
Edit: everything I’m seeing in the developer forums is telling me nothing has changed. Reverting is not as simple as changing that toggle. Once you change that toggle, you will be locked into db1 until a new public release drops… unless you wipe and install the 18.5 ipsw