Apparently, the settings take effect once I click the "Save Changes" button. If later I were click on the settings icon, both import and export checkboxes are shown as ticked.

So I can:
(1) tick the Export checkbox, with the Import checkbox unticked
(2) tick the Import checkbox, with the Export checkbox unticked
(3) tick both the Export and Import checkboxes
(4) untick both the Export and Import checkboxs
and the settings will stick (apply) once I click the "save Changes". However, once I click on the View's settings icon, both checkboxes are shown as ticked - which is confusing.
Reference: https://moodle.org/mod/forum/discuss.php?d=316366