It doesn’t behave just like water. It behaves like a simpler model of water. If you look more closely, the difference isn’t what you’d expect between a good model of water and a bad model of water. It’s what you’d expect between a good model of XeYZn and a bad model of XeYZn.
In other words, it would act like water to a first approximation, but instead of adding the terms you’d expect to make it more accurate, you add the terms you’d use to make an approximation of XeYZn more accurate.
It doesn’t behave just like water. It behaves like a simpler model of water. If you look more closely, the difference isn’t what you’d expect between a good model of water and a bad model of water. It’s what you’d expect between a good model of XeYZn and a bad model of XeYZn.
In other words, it would act like water to a first approximation, but instead of adding the terms you’d expect to make it more accurate, you add the terms you’d use to make an approximation of XeYZn more accurate.