Hi davout,
Yes the reported behavior is present as described.
However when you want to remove tasks from the SmartKanban I suggest you use the removeTask() method.
Quick code example if you want to remove all the tasks in a kanban:

   for(let i = 0; i < this.kanban.dataSource.length; i ++){
                this.kanban.removeTask(i);
    }

More about it you can find in the API of the Kanban:
https://www.htmlelements.com/docs/kanban-api/
Let me know if that works for you!
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team
https://www.htmlelements.com/