Honest gun'riters admit that some sales outfits and manufacturers do specially select guns and other items, to be sent out for review.
Usually, however, these same writers will tell you that the "special selection" is not for beauty or reliability, but rather to make sure that the same specific sample item goes out for testing every time. That way, the sales outfit or manufacturer ends up with only one "slightly used" gun, not a whole bunch of them.
Sometimes this process backfires badly. To read about one notorious incident, click on: The Gun Zone -- The Gunwriting Game