Netflix sends the videos to your computer with a form of DRM and then uses a key from either your browser or hardware to unlock the content. That is nothing like YouTube, which sends both the links and the media to you unencrypted.

My understanding is in general a fixed signature is used, only certain content has the rolling cipher.

If all videos used the same system then youtube-dl would not have had any reason to make major label music videos part of their unit tests.