if you start with a very high gravity liquid and fermented it to the yeasts alcohol tolerance whatever it might be, there would be lots of sugar left in the now finished but extremely sweet wine. after freezing and thawing off the alcohol the remaining liquid would be quite high in sugar.
I read about a guy doing it to a dark beer that he had miscalculated something or other in the recipe. He removed a bunch of alcohol by freezing it and then repitched to the leftover liquid. after that fermented he just mixed the two liquids and bottled it up.
You seem to be under the misunderstanding that the part that freezes will be richer in alcohol. It's the other way around.
Also, what would be the point of starting with a gravity above the yeasts' ability to ferment it? Why not choose a SG that your yeast can handle, and ferment to dry.