Basic algorithmic knowledge questions are not puzzles, and whoever is calling them that is wrong. Those questions still can be stressful, especially for people that don't do well in interview environment, but puzzle is something else. Puzzle is something that requires some non-trivial insight or trick to solve, usually one that the person has no experience with and it is not obvious even for a person with the knowledge of the basics. That's why they are puzzles - they are "puzzling", which the dictionary defines as "confusing" or "baffling".