Atlatl Dart Foreshafts

I thought this insight was of value.  A number of years ago, Bob Berg, of Thunderbird Atlatl, and Atlatl Bob/William Perkins, agreed on a point (which they rarely do) - foreshafts in atlatl darts are ineffective for big game hunting.  There are scores of atlatl foreshafts that have been discovered, along with a few dart shafts without foreshafts, from prehistoric times.  I know I have seen numerous books with line drawings always depicting darts with foreshafts.  Mr. Berg and Mr. Perkins contend - that thru numerous experiments, hunting experiences, and others hunting experiences, that these fore shafts have limitations. A dart, with a foreshaft, will penetrate as deep as the foreshaft.  If the foreshaft is 5-inches, it will penetrate 5-inches, sometimes with the foreshaft breaking at the connection.  Darts without, will penetrate deeper and be more effective in taking big game.  Their conjecture is that darts with foreshafts were more for warfare than hunting.