How it differs from an edit
An edit overwrites; the old value is gone and nobody can tell that an AI answer repeating it was once right. Supersession keeps both, each with its validity period — which is what makes "outdated" a checkable claim.
Example
A backpack sold as 48 litres until 2025 and 45 litres since: the 48-litre fact is superseded, not deleted, and an answer still saying 48 is identifiably repeating the old specification.