Yes, this is the key point: "Changing the license on the data doesn’t retroactively revoke that permission, and the primary impact is on later-arriving actors,

Yes, this is the key point: "Changing the license on the data doesn’t retroactively revoke that permission, and the primary impact is on later-arriving actors, who are typically either smaller start-ups or researchers." And also this: "Mr. Longpre said that one of the big takeaways from the study is that we need new tools to give website owners more precise ways to control the use of their data." This will happen once everything is looted/not needed anymore.