custom field set - defined as TAB - is not displayed on edit pages

i don't know if this is a usability issue, mis-documented feature, or a real bug.

This is a refined issue of my previous issue: http://issues.civicrm.org/jira/browse/CRM-9713

Both in Demo site and on my Wordpress+CIVI personal site:
i defined custom field sets to be displayed as TAB,
but couldn't locate this tab on the Contact Edit page.
I did not find anything on the "right side of the other tabs".

all other custom field sets works as planed.

here's a link to the contact edit page on the demo site:
http://drupal.demo.civicrm.org/civicrm/contact/add?reset=1&ct=Individual

attached - a screenshot of my own site, on which i should've seen an additional hint or tab of the newly created custom fields.