ALTER.. with xmltype silently overwrites row with prior rows data

SET sql_mode = '';

CREATE TABLE t(id INT, s VARCHAR(100));

INSERT INTO t VALUES (1,'<abc>aaaaaaaaaa</abc>'), (2,'a'), (3,'b'), (4,'<c/>');

ALTER TABLE t MODIFY COLUMN s XMLTYPE;

SELECT id, s FROM t;

DROP TABLE t;

MariaDB [test]> SELECT id, s FROM t;

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

| id   | s                     |

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

|    1 | <abc>aaaaaaaaaa</abc> |

|    2 | <abc>aaaaaaaaaa</abc> |

|    3 | <abc>aaaaaaaaaa</abc> |

|    4 | <c/>                  |

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

4 rows in set (0,002 sec)