My guess is that when the videos were uploaded, they were uploaded under a different license than the ones common users use. That license had probably something along the lines of "if you don't agree with new terms, you need to stop using our service" (like TOS).
You know, exactly how Google changes it's term of service and if you don't agree with them you need to stop using their service (usage implies agreement, in this case, though).
If my understanding of the issue is right, then what happened here is: I, label, make a deal with Google saying that I authorize them to display and monetize some videos for x% (where x is agreed by both parties). If I, at some point, no longer want the deal, then Google has no authorization to display my videos. Blocking the videos is simply covering their backs on "You didn't have authorization anymore because we didn't sign the new deal and the old one ended, and you profited from our works by having them on your website".
If this wasn't the case, ie: what was in place was a monetization deal only, then Google could (and it would be the best thing in terms of PR) to simply revert to the monetization everyone else uses because if they uploaded the videos, they agreed to the terms.
Please do correct me if I'm wrong. And do share your opinion.