The way the 'Filter' search works in the 'Tasks' smart folder is that it looks for the specified word typed in any 'tag' (field) in the 'entity' (task).
This means you can not filter by specific fields, unless the field's values are not used in any other field in the task. If the user included the same word/value in any field of the 'Task' that task will be displayed in the filtered table.
For example if you type the word 'submitted' in the 'Filter' to look for tasks in Submitted status, but in the comment field of a Completed status task a user typed the word submitted as part of the description, both the completed and submitted status tasks will be displayed in the table.