Implementation of hook_field_access doesn't allow user to change their own group

Apologies if this is a duplicate, or a misunderstanding, but a use case I'm working with is to allow users to select from a handful of site-wide groups, and change from one to the other as needed. During user registration, this works fine, a user can select which group to join. However, once a member of the site, they are denied access to edit this field by the following logic in og_field_access:

 $field = field_info_field($field_name);
  $settings = $field['settings']['handler_settings'];

  // Check if we are editing the user entity.
  if ($entity_type == 'user') {
    return user_access('administer group', $account);
  }
}

Note that the $field and $settings variables are not used in this function, which made me wonder if this logic is incomplete.

Pointers would be greatly appreciated.