GROUP_MIN_MAX is not applied for LIKE

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (id INT NOT NULL, a VARCHAR(20), KEY(id,a)) ENGINE=MyISAM;

INSERT INTO t1 VALUES (1,'01');

INSERT INTO t1 VALUES (1,'02');

INSERT INTO t1 VALUES (1,'03');

INSERT INTO t1 VALUES (1,'04');

INSERT INTO t1 VALUES (2,'01'); 

INSERT INTO t1 VALUES (2,'02'); 

INSERT INTO t1 VALUES (2,'03'); 

INSERT INTO t1 VALUES (2,'04');

INSERT INTO t1 VALUES (3,'01'); 

INSERT INTO t1 VALUES (3,'02'); 

INSERT INTO t1 VALUES (3,'03'); 

INSERT INTO t1 VALUES (3,'04');

INSERT INTO t1 VALUES (4,'01'); 

INSERT INTO t1 VALUES (4,'02'); 

INSERT INTO t1 VALUES (4,'03'); 

INSERT INTO t1 VALUES (4,'04');

EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a BETWEEN '04' AND '05' GROUP BY id;

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

| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                                 |

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

|    1 | SIMPLE      | t1    | range | NULL          | id   | 27      | NULL |    9 | Using where; Using index for group-by |

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

EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a LIKE '04%' GROUP BY id;

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

| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                    |

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

|    1 | SIMPLE      | t1    | index | NULL          | id   | 27      | NULL |   16 | Using where; Using index |

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