I am presuming that you are doing a series of interviews rather than just one, and conducting a set of semi-structured interviews is by far the most common data collection strategy in qualitative research. So there is no need to give it a label such as mini-ethnography or case study.

It's a decent starting point,IF your source is representative, and IF you will be following that with other interviews. Otherwise, you lack context to evaluate your source and I would recommend against it. Should you ties your wagon to that star, someone may come along a demonstrate that it is falling.