so does it mean that the same varieties of table grapes would be good for making wine if you pick them late? Assuming that grapes unlike bananas don't ripen after they get picked ?
Grapes don't acquire any more sugar once they are picked. They just rot if kept too long without refrigeration.
There are centuries of selection in the varieties of grapes used for wine. They are bred for sugar and taste. So, I'd say that while it's possible to let Table Grapes ripen on the vine and use them to make Wine, you aren't going to get a high quality Wine. Table Grapes are not bred to have the amount of sugar a Wine Grape has.
I suppose that some people don't care that much about taste. After all, people drink applejack. When I've had the time to make Wine, I've always tried to make a Wine that I'm proud to serve to other people. I have dumped Wine that failed my taste test, before anyone else got a chance to taste it. Even with good grapes, bad luck or carelessness will ruin your wine and make it into plonk that is only good for getting people with no taste buds drunk.
Where you make your Wine is important. How clean your equipment is is important. When you stop the fermentation is important. There are lots of opportunities for it to go wrong.
On the Wiki list that I linked there are some varieties that can be used both as a Table Grape and as a Wine Grape. I have never made Wine with one of those varieties, so no idea how good the Wine would be.
