Your post goes hand in hand with exactly what I've been saying since I went online in 1995.
Being able to "sell" and being able to TEACH others to get results are not one and the same. They are not synonymous.
You made one case in point.
Another good example is the bazillions of affiliates that promote marketing programs by saying "the creator of the program made "x" million dollars..." or some other ridiculous claim.
Why aren't the affiliates saying "I make "x" number of dollars?" Because usually - they don't. They buy into great copywriting that does a very fine job of extracting their money from their wallet... but then doesn't do an equally good job of helping them put money back INTO their wallet.