Right, but you can have entries in a block chain that indicate previous entries are no longer valid, or have modifications. Calculating a final state by walking through all the blocks in the chain. ( A bit like a CQRS based system can have a particular state at a point in time by replaying all events up to that point)

Doing it in such a way also makes auditing what's happened much easier since changes are inherently reflected in the chain. You want to know when (or by who if you keep that information) a record changes, it's right their in the chain.