Asking my question a different way: If I have a video that’s shared between two classes (which are variants of each other), and a student watches it in the first class, but then decides to also watch the second class, can the videos which are an intersection between the two classes show up as already-watched when they go to take the second class?
@oedx Not out of the box, currently you would have to use/develop a custom XBlock to share that information across courses, and automatically complete the video when the students display videos that they have already watched in the courses that share it.
You said “use/develop”. Are you aware of anything like that which I could already use, rather than develop?
@oedx No, or I would have mentioned it 
But someone else might?