I've debated this elsewhere and the general premise is that there is thermal "acceleration". As such, the "reason" hot water would freeze faster than cold water (everything else being the same) is that the hot water cools at a faster rate (true because the initial temperature difference is larger) and that it maintains this cooling rate "momentum" so it freezes faster (not true). The problem is that there is no cooling "momentum". When that water reaches the same temperature that the other one was at (previously), it is cooling at the same rate that the other one was when it was at that temperature. It won't cool faster because it had a higher cooling rate previously....all things being equal.