I wonder how they came to those numbers; on a typical stove, if you heat a pot of water to boiling, and then immediately let it cool off, it will spend almost 3 minutes at (or above) 200F (the boiling point of water at 1980 meters) so the sea-level recommendation seems more conservative than the altitude recommendation.
"one minute" is much easier to mentally estimate than "43 seconds" or whatever. Can even be readily timed with an old school analog clock... just wait for it move from one tick mark to the next.
