This seems only tangentially related to the rest of the document so maybe it deserves a more detailed explanation:
Interaction with Inactive Documents (BFCache, Prerendering)
When a session is ended for any reason, any inactive documents which had access to that session's credentials should be destroyed. This ensures that pages in BFCache or that are pre-rendering that contain information guarded by those credentials are not presented after the session has ended.
This seems only tangentially related to the rest of the document so maybe it deserves a more detailed explanation: