Typing 130 vs 90 is 3 button presses vs 2, so the converse would be why type 100 when you could type 60. You can either be a seconds person or a minutes person.
Edit: they entire number entry thing for microwaves is just weird. 60 => 1minute. 100 => 1 minute. 120 => 1minute 20 seconds. Essentially, any 2 digit number is always interpreted as seconds. Which makes me wonder if the Car Talk question wasn't actually "when is 99 > 100"