This is not specific to any industry/sector, but there are interviewers (including myself) who will intentionally ask questions above the technical skill set of the job. The idea is to see where the edge of your knowledge and/or experience is. We expect you to not know some of the answers. In fact, an applicant who can answer every question will not get the job because they are over qualified and I wouldn't expect them to stick around long before they get bored and find a better job. Keeping this in mind has really helped me a lot to not get aggravated or frustrated and to enjoy the interview.
Good luck!
