Are all the AtspiCollectionSortOrder types really a thing?

I see the following in atspi-constants.h:

  /**
   * AtspiCollectionSortOrder:
   * @ATSPI_Collection_SORT_ORDER_INVALID: Invalid sort order
   * @ATSPI_Collection_SORT_ORDER_CANONICAL: Canonical sort order
   * @ATSPI_Collection_SORT_ORDER_FLOW: Flow sort order
   * @ATSPI_Collection_SORT_ORDER_TAB: Tab sort order
   * @ATSPI_Collection_SORT_ORDER_REVERSE_CANONICAL: Reverse canonical sort order
   * @ATSPI_Collection_SORT_ORDER_REVERSE_FLOW: Reverse flow sort order
   * @ATSPI_Collection_SORT_ORDER_REVERSE_TAB: Reverse tab sort order
   * @ATSPI_Collection_SORT_ORDER_LAST_DEFINED: Used only to determine the end of the
   * enumeration.

   *
   * Enumeration used by interface #AtspiCollection to specify
   * the way #AtspiAccesible objects should be sorted.
   *
   **/
  typedef enum
  {
    ATSPI_Collection_SORT_ORDER_INVALID,
    ATSPI_Collection_SORT_ORDER_CANONICAL,
    ATSPI_Collection_SORT_ORDER_FLOW,
    ATSPI_Collection_SORT_ORDER_TAB,
    ATSPI_Collection_SORT_ORDER_REVERSE_CANONICAL,
    ATSPI_Collection_SORT_ORDER_REVERSE_FLOW,
    ATSPI_Collection_SORT_ORDER_REVERSE_TAB,
    ATSPI_Collection_SORT_ORDER_LAST_DEFINED,
  } AtspiCollectionSortOrder;

But looking in collection-adaptor.c it appears that only CANONICAL and REVERSE_CANONICAL are handled. What am I missing?