Adding air to the must is important to the yeast but how much and how it is accomplished varies as you have noted. Personally I aerate my must and wort (when making beer) with nothing more than a drill mounted Fizz-X. The large scale winery introducing air during the fermentation could be due the shear volume of must and yeast to guarantee the cells have plenty of oxygen for budding.
This info below taken from a yeast producer should help you understand why oxygen is important.
<DIV style="MARGIN: 0in 0in 0pt">"Oxygen is a necessary nutrient for proper yeast growth.Yeast requires oxygen for the synthesis of sterols.Sterols are membrane lipids which help maintain cellular fluidity and permeability enabling cells to grow and bud.Every time a cell buds the cellular sterol content is diluted.Once the level becomes too low (in approximately 3-4 doublings) the cells lose the ability to bud.Sterol content generally is the limiting factor of yeast growth.Synthesis of sterols occurs only when oxygen is present. Thus, it is critical to supply the yeast with appropriate levels of oxygen.
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<DIV style="MARGIN: 0in 0in 0pt">Yeast require 8 to 16 ppm of oxygen.Oxygen is typically dissolved into the must during crushing/destemming and then during pump-over/punching down for red wines fermented on skins.The most that atmospheric oxygen can provide to must is about 8 ppm.For this reason, it may be necessary to rack the wine or pump-over shortly after inoculation.
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<DIV style="MARGIN: 0in 0in 0pt">Pure oxygen can also be used to provide adequate oxygen in the must.Oxygen can be injected using a scintered stone.It is important to note that too much oxygen can be added using pure oxygen.Up to 40 ppm can be achieved with pure oxygen, but it is best to keep the dissolved oxygen levels below 20 ppm.
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<DIV style="MARGIN: 0in 0in 0pt">High sugar levels and high must temperatures both make it more difficult to dissolve oxygen into must.For high sugar musts or musts that have high temperatures, additional oxygenation/aeration may be necessary."
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<DIV style="MARGIN: 0in 0in 0pt">~~~~~~~~~ great read thanks ! ~~~~~~~~~~~
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