Joyable Android Engineer interview questions

First interview was a screening interview with the VP. The second interview was a technical interview to design an app to record memories of visiting landmarks. After the second interview I was told they were looking for a full stack engineer. I was interviewing for an Android position not a full stack engineer position. Why are they wasting my time going through the interview process without disclosing what they are looking for. I would steer clear of a company who cannot afford an android engineer and a backend engineer. That is not a scenario that is going to succeed very well.