MySQL 8.0.27 Left Join 一个子查询的问题？

以下代码，a left join b 能查询到数据，c 结果集单独查询无数据。
现在出现了一个诡异的问题：整个 SQL 查询 c.submit_id 既然有数据，应该为 NULL 才对。
如果将 SELECT t1.*, t2.input_name,t2.sort_number 加一个 DISTINCT 就正常了。

SELECT
 a.user_id AS userId,
 b.org_name AS deptName,
 c.submit_id AS submitId,
FROM
 USER a
 LEFT JOIN org b ON a.org_id = b.org_id
 LEFT JOIN (
   SELECT t1.*, t2.input_name,t2.sort_number
   FROM questionnaire_result t1 
   JOIN template_form t2 ON t1.input_id = t2.input_id
   WHERE EXISTS (select 1 from questionnaire_result x where t1.submit_id = x.submit_id and x.questionnaire_id = 'q1' and x.is_deleted= 0 and x.input_id = 't1f1' and x.content_name = '2022-03-241')
 ) c ON a.user_id = c.creator_id
WHERE a.is_deleted = 0

前后执行 explain 对比：

PS：在 10.5.5-MariaDB 没有问题。