The bacteria succeeds in fermenting the wine, but the sulfites are never removed. I wish that I knew more about the chemistry, and perhaps an enologist can comment. My understanding is that although the bacteria introduced converts the sugars, there is still enough sulfite in the to destroy bacteria. For one who drinks wine very moderately, it may not have an effect on the stomach. I have have been known to 2 or three glasses at home after I come home from work. It has often upset my stomach, and given me acid reflex.
Upon thinking about the microbiom and the introduction of sulfites to the stomach, I reasoned that perhaps the wine that I was drinking was killing the good bacteria in my stomach. I remembered that winemaking did not always use sulfites. In fact I know that winemakers of France rely on the bacteria natural in the vineyard. The argument goes that after hundreds and even thousands of years of growing grapes, the natural fermenation is well adapted to the fields of France. In this way I have become a drinker and lover of these French wines.
It is possible that these wines contain a positive bacteria. Since I have been drinking them, I have virtually eliminated my stomach difficulties. Also even on the rare occasion where I have had too much, I feel no hangover in the morning.
I will give a plug to my local Grocery Outlet that has been carring a wide variety of drinkable and some even delictious Bordeauxs. Prices generally range from $6 to $12- Well worth it.