Also to make it more secured you may use display conditions for the secured subpage, that way you can control whether to display attribute's value on the object's list page. You can set it from object -> views -> options -> "Attribute Value protection".
so if a user adds the field to list view, he will not see field's value if he does not meet the display condition criteria.
Without the display condition being used, the field, even if displayed on a secured subpage is always available to be added on object's list page in "configure" option (available fields).
You can set a display condition like show this page to only certain group.