It is more than that. HitBTC has abandoned their central STEEM/SBD wallet. This is the wallet that all STEEM and SBD transfers go in and out of the exchange. Each person has a memo associated with the transfer to know how much of the balance each person has. Why has HitBTC abandoned their wallet? No one knows. It could be this way forever. It is like HitBTC has lost the keys to the wallet. What they have done is created a virtual supply based on the deposits people have made. They have a virtual supply of STEEM and a virtual supply of SBD that they trade with. The problem is that since they abandoned the wallet which has the real STEEM and SBD in it, then what are they trading? It is fake money.

Poloniex has done the same thing.

When they go to get audited, they are going to have a difficult time explaining why they were trading a fake currency against Bitcoin.