It's a technical interview to assess your technical knowledge. The idea is you'd have another interview with your boss about your teamworking skills and similar rubbish.

I can actually see a need for this, but they need to get more experts than "our mates from nearby startups and their parents."

Also the subjects they've listed are all for programming topics when I doubt you're going to be in the situation of not already having some in house experts. They need much more niche subjects.