When columnstore_use_import_for_batchinsert=ALWAYS, rollback does not work

MariaDB [tpch1]> create table region1

  ->  (

  ->   r_regionkey int,

  ->   r_name char(25),

  ->   r_comment varchar(152)

  ->  ) engine=columnstore;

Query OK, 0 rows affected (0.281 sec)

MariaDB [tpch1]> start transaction;

Query OK, 0 rows affected (0.000 sec)

MariaDB [tpch1]> insert into region1 select * from tpch1.region;

Query OK, 5 rows affected (1.571 sec)

Records: 5 Duplicates: 0 Warnings: 0

MariaDB [tpch1]> rollback;

Query OK, 0 rows affected (0.005 sec)

MariaDB [tpch1]> select * from region1;

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

| r_regionkey | r_name   | r_comment                                                      |

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

|      0 | AFRICA   | lar deposits. blithely final packages cajole. regular waters are final requests. regular accounts are according to |

|      1 | AMERICA   | hs use ironic, even requests. s                                           |

|      2 | ASIA    | ges. thinly even pinto beans ca                                           |

|      3 | EUROPE   | ly final courts cajole furiously final excuse                                    |

|      4 | MIDDLE EAST | uickly special accounts cajole carefully blithely close requests. carefully final asymptotes haggle furiousl    |

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

5 rows in set (0.011 sec)