I understand this, but good lord people need to stop bringing this up in every damn thread that mentions Ethereum.
We all know about the DAO and what happened afterwards.
The chain still includes the transaction history of what happened with the DAO, but the hard fork added a special case unique state change which undoes most of the effects of the transactions that happened with the DAO.
So, the transactions still are recorded as having happened, but the state was edited?
Not that that necessarily is a particularly important distinction, but I think it is one that can reasonably be made.
You can't just throw out or dismiss the historical failures of the model because it doesn't fit the ongoing narrative. The DAO was a glimpse at how easy the theory is corrupted, whether it started for the right reasons or not.