>> They want people who can work under stress.

Not exactly. Interviews are a different kind of stress that is usually a direct result of being observed in an unfamiliar and somewhat high pressure situation. You might have to deal with an outage at work, but typically your employment isn't on the line (less pressure) and you have a great deal more familiarity.

Some hiring practices intentionally try to create a more welcome, less stressful experience because they don't want to bias for interviewing skill (as opposed to fitness for the job).