until 和过去完成时的的用法

题目

until 和过去完成时的的用法
he stayed here until i came back和he had stayed here until i came back有什么区别?
过去完成时是过去时的分支还是完成时的分支?

答案

he stayed here until i came back:他并不是专门,特意等我；二人相差时间不多
he had stayed here until i came back 专门,特意等我,他等我时间较长