Why show pre hack balance unless planning on all accounts sharing in loss of stolen coins also doesn't make sense that eth would be missing from Balances since there pre hack balances
What is showing is exchange ledger balances. It does not reflect what is held in the exchange wallet.
Centralized exchanges don't hold individual user funds for each user. When you deposit to your individual address the amount is "swept" and moved to an exchange hot wallet or cold wallet. The individual balance is shown is what their database shows you have deposited according to their records. Any trades occur on their database (not on the blockchain)
It does not show what they have in their exchange wallet.