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.
I don't upload YouTube videos so I'm unsure about the logistics of settings for videos. Do you get these options on videos already uploaded or is this only an option when first uploaded? Is this for the whole channel or video specific? Just curious how it works. Regardless if they ever decide to turn it on by default that would mean YouTubers would have to go through hundreds of videos and turn it off individually unless it's a channel wide setting kinda thing.
Edit: Just noticed it's under channel settings so I guess that's a good thing. If it was video specific that would be just plain evil. I guess I shouldn't give them ideas...