A seeded scenario: Acme Corp moved its headquarters. The 2019 filing said Boston; the 2022 filing said Denver. Drag the system-time slider to replay what the ledger knew at any past moment. Later corrections never leak into the past: that is the un-knowing invariant.
Plain RAG answers “what is true now.” A bi-temporal ledger also answers “what did we believe then”, because every fact carries two independent time axes: when it was true in the world, and when the system learned it.