Just my take on this:
In many areas of Europe where grapes have been grown for hundreds, if not thousands of years, natural yeast has developed in the area that is good wine yeast. After all, the wine was made in the same area and the yeast that will ferment good high alcohol wine would multiply best in the wine. The must is then spread back to the soil so you are culturing yeast between the winery and the vineyard and end up with good wine yeast dominating. It is not actually wild yeast anymore. Now if you get your grapes from one of these areas, you have a real good chance of having a good ferment from the yeast on the grape skins.
Oxidation reductionI've become a more proficient taster since I've starting the hobbies of winemaking and homebrewing. Awhile back, I made a batch of Chilean Merlot from a kit. I've since decided the wine had oxidized noticeably...
If you are getting your grapes from some area in the US where grapes have not been grown for hundreds of years and where the wine may not be made in the vineyard and the pumice may not be spread back in the field ... it may be a bit more iffy. But it will probably still work.
Then again, good wine yeast is cheap. Grapes and time are expensive. Why take chances. I buy yeast.
Ray
