Unless things have changed since I left the industry, because of the dropout rate in manufacture they manufature to the full spec, test, sort according to the test - for example in the days of floppy disks most manufaturers manufactured as quad density, and according to the testing were marketed as quad, double or single density. I would expect that the same principles pertain to chip manufacture. It makes sense and ensures that as much product as possible reaches the market place - the more that goes in the bin raises the price of the product to the customer. Early colour laptop screens had a manufacture drop-out rate as high as 98% in the early days hence the very high price!