Normal fermentation won't reach high alcohol levels. The alcohol eventually stops the fermentation. Sugars are converted to alcohol and late picked fruit (as u say) has more sugar (and Less ACID). Alcohol makes the Product last longer. Preserves it . Post bottling fermentation will produce sediments ( lees) in the Bottle and sometimes some small bubbles. (spritzig). Not really a sort after result. As a general practice , DON'T keep whites too long. Champaigne (Fermented in Bottle) and labour intensive often is earlier picked and therefore More Acid. Some growers pick early to reduce losses due to birds like silver eye and starlings which play havoc with the crops. Nev