It doesn't.
Won a bet on this in 1980
with a friend who always filled
the ice cube trays with hot water.
I understand that you can make the
hot water win in a vacuum at the speed
of light in the presence of 2 blind cats
and some green crystals but if you want a
cocktail in a hurry fill the trays with cold
water
I've spent my whole life under the impression that was a well-known myth of science. An old wive's tale. Silly, unscientific people fill their ice cube trays with hot water under the mistaken assumption that it will freeze faster that way. But people who understand science know that the hot water needs to become cold water before it becomes frozen water, so starting with cold water will give you a head start and will get you to frozen water faster.
For 40 years I've been told that the "hot water freezes faster" thing is a myth.
I feel that this "contest" is meant to be a joke.