you cannot use a blanket update or delete link like this.
the update or delete links must be part of a results set.
If you look at the dataassist results page, the links to the updaate and delete pages pass the record id as a querystring variable.
This tells the update and delete page what record is being updated or deleted.
without passing the record id, the update or delete page has no way of knowing what record to update or delete.
perhaps this is a work flow that may make more sense to you:
run the data assist wizard once to create the public page.
Leave the page names as they are, but uncheck the option to create the insert, update and delete pages.
Run the DataAssist wizard a second time to create the admin pages and add "admin/" in front of the page name "admin/users_insert.php" for example
This will create the pages in a directory named admin
dont uncheck the insert, update and delete options this time.
Use security assist to add restriction to this second set of pages.