Set log-slow-verbosity=explain was not working

Trying to enable slow_query with verbosity enabled with different options in Mariadb 10.6.*. But unable to set option- explain for log-slow-verbosity in mysql session https://mariadb.com/kb/en/explain-in-the-slow-query-log/ while we can set other options as query_plan and innoDB in mysql session

> set log_slow_verbosity=explain;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'explain' at line 1

> set log_slow_verbosity=query_plan;
Query OK, 0 rows affected (0.009 sec)

> set log_slow_verbosity=innodb;
Query OK, 0 rows affected (0.038 sec)

> show variables like '%slow%';
+------------------------------+------------------------------------+
| Variable_name                | Value                              |                                                                                                 
+------------------------------+------------------------------------+
| :::                          |                                    |
| log_slow_verbosity           | query_plan                                                                                                                                                                                                                                                        
| slow_query_log               | ON                                                                                                                                   
| slow_query_log_file          | /var/opt/na/log/mysql-1/slow-query.log                                                                                               
+------------------------------+------------------------------------+

And while the same is working fine when we set this variable as part of my.cnf file

> cat /etc/na/my-1.cnf | grep log-slow
log-slow-verbosity=query_plan,explain

> show variables like '%log_slow%';
+------------------------------+------------------------------------+
| Variable_name                | Value                              |                                                                                                 
+------------------------------+------------------------------------+
| log_slow_verbosity           | query_plan,explain                                                                                                                   |
+------------------------------+--------------------------------------------------------------------------------------------------------------------------------------+
6 rows in set (0.001 sec)

Is this option not supported in 10.6 which is not mentioned in the docs or am i missing anything https://mariadb.com/kb/en/slow-query-log-extended-statistics/