If you freeze water with substances dissolved in it, and let it sit, the ice crystals slowly push the substances into small areas that remain liquid. Eventually there will be regions of ice that are solely water, and slushy regions full of - whatever.
That's how cold distillation works: you take a fermented liquid, let it freeze, then pick out the ice. There are limits to how concentrated it can be, which is why people also use heat-driven distillation, but it's a traditional method in very cold regions of the world where cold is free in winter.
It's part of why making homemade ice pops with juice is challenging - the water tends to separate from sweet juicy syrup that forms.
In warm regions/periods, cold isn't cheap - but if you're going to make a frozen concentrate, why not make ice at the same time, instead of expending all that energy to produce steam you're not going to use?