... since S have V-en

完了と継続の用法があるとゆーだけの話でしょ

>>353
>A "It's been a while since he died."
>B "It's been a while since he has died."
>この場合、Aのみが正解になります。

これはネイティブに確認とったんかい
完了に解せばBは当然ありじゃん