Youtube API's change frequently, but rarely in backwards incompatible ways.
After all, youtube runs on millions of client devices which can't or won't update the client application. Eg. Android devices with google play broken or logged out. Forcing those users to update in many cases will lose a user. A 5+ year old phone's copy of youtube still runs and plays videos.
Now the API's that the website uses... those can be updated with nearly zero notice...