Just saw the notification for this in my Youtube Studio. For now it seems as if this setting is turned off by default, but for anyone like myself who uploads videos to Youtube, I recommend checking that they don’t decide to toggle this on for you in the future.
The youtube videos have already been used to train AI. MKBHD proved it when sora crapped out his own plant in a generated “tech video”. The question is whether google allowed it or not.