Some manufacturers use the same print, but different gray-goods to print them on. I've bought Wal-Mart stuff to match something I had gotten at Hancock's and the difference was clear once they were washed. I always hit those red-dot Joanne specials, too, and have noticed the quality has been getting very iffy on some.
I don't think I've ever seen the unknown content label anywhere buy Wally World though - I have a feeling they recycle the cardboard centers.