Wrong results with xmltype as a virtual column

CREATE TABLE t1(a VARCHAR(50), b XMLTYPE AS (a) VIRTUAL);

INSERT INTO t1(a) VALUES('<yyyyyyyyy>xxxxxxxxxxxxxxxxxxx</yyyyyyyyy>');

INSERT INTO t1(a) VALUES('a');

INSERT INTO t1(a) VALUES('b');

INSERT INTO t1(a) VALUES('<dddddddddd>tttttttttttttttttttttt</dddddddddd>');

INSERT INTO t1(a) VALUES('e');

SELECT * FROM t1;

DROP TABLE t1;

MariaDB [test]> SELECT * FROM t1;

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

| a                                               | b                                               |

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

| <yyyyyyyyy>xxxxxxxxxxxxxxxxxxx</yyyyyyyyy>      | <yyyyyyyyy>xxxxxxxxxxxxxxxxxxx</yyyyyyyyy>      |

| a                                               | ayyyyyyyyy>xxxxxxxxxxxxxxxxxxx</yyyyyyyyy>      |

| b                                               | byyyyyyyyy>xxxxxxxxxxxxxxxxxxx</yyyyyyyyy>      |

| <dddddddddd>tttttttttttttttttttttt</dddddddddd> | <dddddddddd>tttttttttttttttttttttt</dddddddddd> |

| e                                               | edddddddddd>tttttttttttttttttttttt</dddddddddd> |

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

5 rows in set, 3 warnings (0,001 sec)

Warning (Code 1292): Incorrect XML value: 'a'

Warning (Code 1292): Incorrect XML value: 'b'

Warning (Code 1292): Incorrect XML value: 'e'