Correcting an accounting error after the fact is something that couldn't be done in the real world prior the blockchain entered the scene.

Unilaterally false. Correcting accounting errors happen all the time, and its difficulty does not stem from any technological barriers, it is strictly due to the fact that in the current banking system, everyone has their own ledger, and because it is decentralized (you sense the irony here?) to this level having everyone roll back changes requires a lot of coordination. It certainly can be done, and has been done. Blockchain did nothing miraculous here save from using one ledger database, and thus making widespread roll backs of transactions easier.