A more mundane explanation is that hot water evaporates faster than cold, decreasing its volume and thus the time it takes to freeze.
[Edit - Cannot delete my comment now. As 'ketzo' points out below my point is not same as OP's. OP points out that hot water is less dense. Maybe less dense liquid cools faster]
The first seems compelling to me, less mass means less over all energy to freeze.
The second less so. Hot water has a bigger surface area, which makes heat loss fast at first. When it gets to cold water's temp it should have the same surface area as the cold water making the advantage disappear.
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),
It would be pretty wild if they were immediate! But.. if you keep it moving at say -1, will it still eventually freeze? I struggle to imagine but don't know why really. Maybe it means something like that. Not that I know why that would be unique to water either.
Water isn't strange. It's state changing is what's interesting. That's where the most energy is converted. From latent hidden energy instead of specific heat.
A more mundane explanation is that hot water evaporates faster than cold, decreasing its volume and thus the time it takes to freeze.
[Edit - Cannot delete my comment now. As 'ketzo' points out below my point is not same as OP's. OP points out that hot water is less dense. Maybe less dense liquid cools faster]