Global Center on Adaptation interview questions

The interview consists of a long process of 1 written test and two interviews. The written test was 3 hours long and that itself is a red flag in a company- to use people's time to make project proposals etc and make them do unpaid labour. After this stage I heard back from them after months saying I was not selected. When I look at the company website the position is not filled and they advertise for more positions. Could it be a ghost listing made to make people to unpaid labour? this is a pathetic tactic many companies are using nowadays. Be careful.