The AI Cleanup feature requires you to actively choose to start the process in a note. So unless you tap the AI Cleanup button it does not start. However, once underway you have to allow the process to be completed.
If you have previously chosen not to show the second confirmation screen then I'm not sure what happens. Perhaps what you describe. If, like me, I have not chosen to hide the confirmation screen, then there's is a cancel button to the top right.