LIMIT and ORDER BY clause is ignored on a query with UNION when using brackets

CREATE TABLE t1 (b int);

INSERT INTO t1 VALUES(1),(2),(3),(4);

CREATE TABLE t2 (b int);

INSERT INTO t2 VALUES (4),(5),(6),(7);

(select b from t1  UNION select b from t2) limit 1;

(select b from t1  UNION select b from t2) order by b desc;

MariaDB [test]> (select b from t1  UNION select b from t2) limit 1;

+------+

| b    |

+------+

|    1 |

|    2 |

|    3 |

|    4 |

|    5 |

|    6 |

|    7 |

+------+

7 rows in set (0.001 sec)

MariaDB [test]> (select b from t1  UNION select b from t2) order by b desc;

+------+

| b    |

+------+

|    1 |

|    2 |

|    3 |

|    4 |

|    5 |

|    6 |

|    7 |

+------+

7 rows in set (0.001 sec)

MariaDB [test]> (select b from t1  UNION select b from t2 limit 1);

+------+

| b    |

+------+

|    1 |

|    2 |

|    3 |

|    4 |

|    5 |

|    6 |

|    7 |

+------+

7 rows in set (0.002 sec)

expected :

MariaDB [test]> select b from t1  UNION select b from t2 limit 1;

+------+

| b    |

+------+

|    1 |

+------+

1 row in set (0.001 sec)