Incorrect usage of CUBE/ROLLUP and ORDER BY with GROUP_CONCAT(a ORDER BY a)

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT);

INSERT INTO t1 VALUES (10),(20),(30);

SELECT a,GROUP_CONCAT(a ORDER BY a) FROM t1 GROUP BY a WITH ROLLUP;

+------+----------------------------+

| a    | GROUP_CONCAT(a ORDER BY a) |

+------+----------------------------+

|   10 | 10                         |

|   20 | 20                         |

|   30 | 30                         |

| NULL | 10,20,30                   |

+------+----------------------------+

SELECT a,GROUP_CONCAT(a ORDER BY a) FROM t1 GROUP BY a WITH ROLLUP HAVING GROUP_CONCAT(a ORDER BY a)='10,20,30';

SELECT * FROM (SELECT a,GROUP_CONCAT(a ORDER BY a) FROM t1 GROUP BY a WITH ROLLUP HAVING GROUP_CONCAT(a ORDER BY a)='10,20,30') t1;

SELECT (SELECT GROUP_CONCAT(a ORDER BY a) FROM t1 GROUP BY a WITH ROLLUP HAVING GROUP_CONCAT(a ORDER BY a)='10,20,30');

ERROR 1221 (HY000): Incorrect usage of CUBE/ROLLUP and ORDER BY