I think your estimate of interviews as a "medium stress situation" is somewhat simplified and personal. Interviews push you into completely unfamiliar territory, in which you're simultaneously trying to solve context-free problems, defend your answers, and gauge the personality and preferences of your interviewer (an answer that works for one won't always work for another).

A client meeting, code review, or dispute with a manager can be stressful, but you can answer from a position of strength. You know your code, have reasons for your decisions, and have met some standard to get the job. Interviews may be less demanding, but for some people it's a huge problem that there's no solid place to stand.