I think SPS’s online interviews are just all pretty short in general (mine went for a bit more than 22 minutes). In terms of your interviewer, I would say that is pretty odd. My interviewer was fine. She took notes, asked if my parents had questions (to which i kindly responded with a no since my parents do not speak much English), and said stuff like “oh i think you will be a great addtions to our community” or “seems like you know us quite well” (appears quite generic to me). Anyways, I don’t think you should worry about the length of your interview, and good luck!