Group content yes, but what about your own stuff?

Perhaps it's an edge case, but for example if I was collaborating on something, or for example submitting coursework, I would be thinking this is "mine", but if it is shared with others via the group, it could become available as soon as I left that workgroup or the group dissolved.

Ignore what I said about owner/container, I was sleepy, but I think the owner should always have access...