Ensure that the category in the flow does not have the edit permission in the All People - Own’s data permission group.
You can do that by navigating to Settings > Account > Permissions Groups > All People - Own’s data > People's data > scroll to the category in the flow > disable/ uncheck Edit permission,
We are trying to ensure that the changes are carried out using the flow not via normal edit permission.
Please note: If the request is made on the profile by another user it will not trigger. The request will only go through to an approver if the user makes the request themselves or if an admin logs in as the user. Admins cannot use Self Service flows since their profiles override the approval needed.
For more information, feel free to refer to the Help Center article.
