Off Market // Pocket Listings and how they're used

Several company's and associations are trying to rid the real estate world of pocket listings.  Stating that they do a disservice to the seller of the home.  Statistically the home values average less when they sell off market.  But the data for off-market sales isn't always available so the numbers are likely skewed.  Does listing your home off-market really deter you from reaching your financial goals?  Or is the old adage true here as well... The devil is in the details.