もう一つ

https://www.gadgetsnow.com/amp/slideshows/google-photos-ending-free-storage-on-june-1-all-your-questions-answered-on-whats-changing-whats-not-and-more/photolist/83021090.cms

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What happens to your photos if you cross the limit?
If you have used all of your storage, you won't be able to back up new files in Drive. After June 1, you will be unable to save any additional photos and videos in your Google Photos account. You won’t be able to send or receive messages in Gmail. Messages sent to you will be returned to the sender.

そもそも6/1以降にアップロード開始しても15GB以上の超過状態は作れない
だから上記で述べた2年以上15GB以上の状態削除対象とは過去アップロードした物も含まれるってこと