I suspect that yeast don't need the sugars to be inverted to be able to consume and ferment them. They prefer glucose because it is a little easier to ferment than sucrose so in any solution the yeast go after glucose before sucrose. But that's a lot like us: we , as a species, tend to prefer to consume simple sugars to complex carbohydrates.
My guess is that the struggle the yeast had to ferment the sugars in solution (the must) was because sugars in and of themselves ce any of tontain very few of the compounds yeast need to be able to reproduce and repair cell structures. Yeast need nitrogen , oxygen, B vitamins, amino acids, calcium, potassium, zinc, and magnesium and many other trace metals and minerals. Sugar is a nutritional desert for yeast. Malted barley (wort) is not, so brewers rarely have to worry about feeding the nutritional needs of yeast, but wine makers can rarely avoid this, though some fruit is naturally rich in these compounds. Table sugar and honey are not.
