FAPI startup guide not branched for D5

well, at first I though there was no branch done for D5 of the following document:
http://api.drupal.org/api/file/developer/topics/forms_api.html/6
but looking more closely, if found there is a D5 version:
http://api.drupal.org/api/file/developer/topics/forms_api.html/5

the bug is that the tabs for D5, D6 do not appear like in other pages, e.g.:
http://api.drupal.org/api/file/developer/topics/forms_api_reference.html/6