JSON_UNQUOTE returns incorrect results depending on the collation

MariaDB [(none)]> SELECT VERSION();

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

| VERSION()       |

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

| 10.2.10-MariaDB |

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

1 row in set (0.00 sec)

MariaDB [(none)]> SET @`json` := '{"sv":"Börk"}';

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SELECT

    ->   JSON_UNQUOTE(

    ->     JSON_EXTRACT(CAST(@`json` AS CHAR CHARACTER SET latin1), '$.sv')

    ->   ) `latin1`,

    ->   JSON_UNQUOTE(

    ->     JSON_EXTRACT(CAST(@`json` AS CHAR CHARACTER SET utf8mb4), '$.sv')

    -> ) `utf8mb4`;

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

| latin1  | utf8mb4 |

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

| "Börk"  | Börk    |

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

1 row in set (0.00 sec)

mysql> SELECT VERSION();

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

| VERSION() |

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

| 5.7.20    |

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

1 row in set (0.00 sec)

mysql> SET @`json` := '{"sv":"Börk"}';

Query OK, 0 rows affected (0.00 sec)

mysql> SELECT

    ->   JSON_UNQUOTE(

    ->     JSON_EXTRACT(CAST(@`json` AS CHAR CHARACTER SET latin1), '$.sv')

    ->   ) `latin1`,

    ->   JSON_UNQUOTE(

    ->     JSON_EXTRACT(CAST(@`json` AS CHAR CHARACTER SET utf8mb4), '$.sv')

    ->   ) `utf8mb4`;

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

| latin1 | utf8mb4 |

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

| Börk   | Börk    |

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

1 row in set (0.00 sec)