date_api_filter_handler can't find what views_handler_filter_date can see

little update,

I tried it all in it's own module using hook_date_api_fields() and the code above (and adding uc_shipments as the base table) and there is no difference...it seems I'm really missing something or there is a slight bug...the field I'm working with here is uc_shipments.ship_date (courtesy of ubercart) which is a UNIX timestamp. my hook_date_api_fields() looks like this (note: i've tried without the switch):

function uc_views_shipments_date_api_fields($field) {
  $values = array(
    // The type of date: DATE_UNIX, DATE_ISO, DATE_DATETIME.
    'sql_type' => DATE_UNIX,
    // Timezone handling options: 'none', 'site', 'date', 'utc'.
    'tz_handling' => 'site',
    // Needed only for dates that use 'date' tz_handling.
    'timezone_field' => '',
    // Needed only for dates that use 'date' tz_handling.
    'offset_field' => '',
    // Array of "table.field" values for related fields that should be
    // loaded automatically in the Views SQL.
    'related_fields' => array(),
    // Granularity of this date field's db data.
    'granularity' => array('year', 'month', 'day', 'hour', 'minute', 'second'),
  );
  switch ($field) {
    case 'uc_shipments.ship_date':
      return $values;
  }
}

And in uc_views_shipments.views.inc

/**
 * Implementation of hook_views_data().
 */
function uc_views_shipments_views_data() {
  $data = array();

   // Definitions for uc_shipments
  $data['uc_shipments']['table']['group'] = t('Ubercart shipping');
  //serial
  $data['uc_shipments']['table']['base'] = array(
    'field' => 'sid',
    'title' => t('Ubercart Shipments'),
    'help' => t('Order Shipment Details'),
    'weight' => -10,
  );
  // Add shipping details to uc_views
  $data['uc_shipments']['table']['join']['uc_orders'] = array(
    'left_field' => 'order_id',
    'field' => 'order_id',
  );
  $data['uc_shipments']['sid'] = array(
    'title' => t('Order Shipment ID'),
    'help' => t('The shipment id.'),
    'field' => array(
      'handler' => 'views_handler_field_numeric',
      'click sortable' => TRUE,
    ),
    'sort' => array(
      'handler' => 'views_handler_sort',
    ),
    'filter' => array(
      'handler' => 'views_handler_filter_numeric',
    ),
  );
  $data['uc_shipments']['carrier'] = array(
    'title' => t('Shipping Carrier Title'),
    'help' => t('The shipping carrier used.'),
    'field' => array(
      'handler' => 'views_handler_field',
      'click sortable' => TRUE,
    ),
  );
  $data['uc_shipments']['cost'] = array(
    'title' => t('Shipping Cost Amount'),
    'help' => t('The shipping actual cost.'),
    'field' => array(
      'handler' => 'uc_views_handler_field_money_amount',
      'click sortable' => TRUE,
    ),
  );
  $data['uc_shipments']['ship_date'] = array(
    'title' => t('Order Ship Date'),
    'help' => t('The shipment date.'),
    'field' => array(
      'handler' => 'views_handler_field_date',
      'click sortable' => TRUE,
    ),
     'sort' => array(
      'handler' => 'views_handler_sort_date',
    ),
    'filter' => array(
      'handler' => 'views_handler_filter_date',
    ),
  );
  //if the sleeker date module is installed use that for filtering
  if(module_exists('date_api')) {
    $data['uc_shipments']['ship_date']['filter']['handler'] = 'date_api_filter_handler';
  }
  
  return $data;
}

Again, it is available as a filter, uses the date api filter handler but the field is not listed in the "filter by" fields (see attached)