The article is correct. IB asked for $30 margin for long positions, they thought price can't go below 0, so there was no risk, so no need for a margin. Remember margin is calculated with SPAN method, that consider 16 scenarios of risk, there was no risk scenarios in IB calculations, so no margin.

Margin for futures is not fixed, it's dinamically calculated taking in consideration all scenarios in which you can lose money, and price can go against your position. For this contract, IB thought minimum price was 0, they also told that to their customers: contract specs said that. So as they bought at 0.01, there was not possibility that they could lose money, price could only go up. So IB asked for $30 margin as Bloomberg says. The result, the clients lost 1250 times their margin.