It's true for first-order phase transitions but not for second-order phase transitions. The article actually talks about it further down: > the Mpemba effect c

It's true for first-order phase transitions but not for second-order phase transitions. The article actually talks about it further down: > the Mpemba effect could happen through a related mechanism that Raz has previously described with Lu in systems that undergo a second-order phase transition, meaning that their solid and liquid forms can’t coexist at the same temperature. Water is not such a system (it has first-order phase transitions),