This is going to be fun!
What happens if I am watching a video with my family using this URL. And someone across the world is also watching the same video with his/her family using the same technique. Now we have two families sharing the same video, isn't it?
Regardless of how many different sets of people are watching the same youtube video, it would still be a private screen where only people with your family's unique co-watching URL can join or watch it.
That way the co-watching experience remains private. It will be a separate private screen for your family and theirs.
Thank you for bringing this up and letting me answer this for others too :)
Thanks for trying it out.
All co-watch URLs are unique and is with only with the host (the one who initiates the co-watch) in the beginning.
If you share the URL with your friends, they will be able to join irrespective of how late they are into the party.
Thanks for trying it out. Whole of this is just the Youtube loaded in an iframe. Video chat is implemented via browser WebRTC. The requests you mentioned would be almost equivalent to what you would notice while watching a youtube embed.
No idea what made you think think that it is not private. Would be of great help if you can raise the concerns here for us to fix if there's any. Happy to chat.