Thanks for spreading the word even more.
I highly doubt casual spectators are on Penguin looking at marked deck pictures. They have their own problems to worry about. This is just a case of magician's over-paranoia. Sure they should not have the exact method shown but magicians are the only ones looking for that.
But if a layman was really determined to find out how marked decks work they could anyway, or just buy them and see how they are marked. The key is performing it well enough that they don't suspect a marked deck, and even if they do you should be able to switch it out easily. I agree that they probably should not be showing the exact method but I am also not frightened about it.