If one thought the worst of people, one could speculate if the publishers therefore would be inclined to send the books that failed QC to the libraries?
That reminds me of some photo book publisher selling defective copies of some titles at a very reduced rate. I think it was mentioned in a thread on here, somewhere. In that instance, perhaps a page or two had a printing error (a blot or a smudge or a weird line). For an entire copy to end up substandard would be odd.
