It does sound like B.S. ....
until you're standing downstream of one of these guys and they are absolutely wearing them out. Seeing is believing, my friend.
Also, most of these guys (when asked) will gladly tell you where they caught them, how they caught them, and will usually give you a handful of flies.
"Don't confuse ignorance with a point of view." - Dilbert
"Many men go fishing all of their lives without knowing that it is not fish they are after."~Henry David Thoreau