Restaurants who do that can acquire very high quality goods at very low prices, in the same way that a tailor can produce you fantastic clothes at a reasonable price. Understanding inventory risk makes it clear why this is so: a producer can't afford to spend a lot to produce a premium product that goes unsold. The rational thing to do is to produce only that which can surely be sold profitably, which reduces the risk, but also keeps the cost to the consumer high.
Some restaurants, like The Herbfarm, raise their own hogs. That not only ensures they've got the price and availability, but they can control the finishing of the hogs to get the best raw material. Because they'll be processing the pork, they want to control the finish. To that end, they are feeding the hogs things like acorns, which are high in tannins, antioxidants and monounsaturated fats.
The best Spanish producers of jamon likewise contract for very special pork - as otherwise it won't get produced at all. In contrast, almost all American processors just buy spare unwated spare parts (e.g. hams), ensuring that their raw material and end results are mediocre, regardless of what processing methods they use.
There's also an article, "A French Family Dynasty Reinvents the Oyster", about a French oyster company and the methods they use to consistently produce the best oysters:
Oysters are then trucked here to be finished and packed. They spend several weeks in oyster ponds, with water changed regularly and salinity measured carefully, before being washed and sorted by size.It doesn't surprise me that it takes controlling chemical variables like salinity to make the best raw material; pigs are the same (but its the fat and flavor to control). You can eat Mangalitsa pigs fattened on different farms and they'll taste better or worse.
I certainly hope that when the "New York Times" writes about American Mangalitsa producers, they'll be fair and say we are reinventing the pig - because the fundamental things required to produce the best pigs aren't that different from those required to produce the best oysters.