If you want to redefine "rollback" as "any fork that changes a blockchain's data" then ok, but that seems like a misleading definition to me. Normally a rollback means "all transactions are rolled back," which has entirely different consequences. In Ethereum's case, the data afterwards is different even from a rollback/reapply, since the theft is still in the transaction history.

In any case it seems fairly useless to debate what the meaning of "rollback" should be.