QueryBuilder: union and order by not works

I have:

$query1 = (new \yii\db\Query())
    ->select("id, category_id AS type, name")
    ->from('post')

$query2 = (new \yii\db\Query())
    ->select('id, type, name')
    ->from('user')
    ->orderBy('type');

$query1->union($query2);

This code generates the following SQL:

(SELECT `user`.`id`, `user`.`category_id` AS `type`, `user`.`name` FROM `post`) 
UNION
(SELECT `user`.`id`, `user`.`category_id`, `user`.`name`  FROM `post` ORDER BY `type`) 

The SQL above does not order correctly.
It's necessary remove the parentheses. Ex:

SELECT `user`.`id`, `user`.`category_id` AS `type`, `user`.`name` FROM `post`
UNION
SELECT `user`.`id`, `user`.`category_id`, `user`.`name`  FROM `post` ORDER BY `type`

Start at the QueryBuilder union and orderBy SQL-generation paths and reproduce the query shown in the issue. Compare the generated SQL with the expected unparenthesized UNION output; done means the ordering behavior matches that example.