> Ethereum Classic is a fork of Ethereum that held blockchain is immutable paradigm

Ethereum Classic did a hardfork last October which removed null accounts created in the DAO attack. Now, while this didn't change account balances, these were legally created accounts and the historical ledger was changed. The hardfork was controversial at the time for this reason.

You can't say that in Classic the blockchain is an immutable paradigm - it changed history just as Ethereum did.