I responded to this same topic in the BOW section but I think its worth saying again.
Organizations like P&Y and B&C and SCI etc. are private clubs and as such they drafted a charter and passed bylaws. They have the perogative to decide under which circumstances an animal is acceptable for entry into their organizations record books. If 65% letoff is the standard then thats how it is until the voting membership of P&Y changes it to something different.
P&Y outlawed electronic devices attached to a bow and some folks are pissed about that too. I've seen posts at other sites where guys complained that the animals they shot in Africa were ineligible for P&Y because they're from Africa. Well guess what? Both P&Y and B&C have "North American Game" in their titles.
P&Y was wise in my opinion, to put equipment restrictions in place. Bow hunting has already gotten out of hand. P&Y saw the writing on the wall, as it were and attempted to use their influence to try and stem the increasing flow of gimmicky gadgetry that was rapidly infecting archery hunting.
Look at any bowhunting magazine. Half the pages are adds for all kinds of gizmos and/or bows that are designed to make you a "better" bowhunter with less effort. Now thats what its really all about, ain't it? Less Effort! Sure, the basic dynamics of drawing and holding the string at full draw with muscle power are still in place BUT if a device were invented that drew the bow for you, held it at full draw and shot it with accuracy, there would be a faction of so-called bowhunters who would absolutely scream that this new device is necessary.
Please remember that bowhunting was reintroduced by hunters who wanted more challenge from their hunting and so chose to hunt with a weapon with decidedly lesser capabilities than a rifle(in terms of effective range). It seems to me that every single innovation since then has been specifically designed to close the gap between rifles and bows.
If not for groups like the Pope and Young Club there would be heat-seeking arrows for sale because people, Americans in particular, don't ever know when to leave well enough alone.
Somebody, somewhere had to draw a line. The Beatty buck is still a fantastic animal regardless of whether or not it "qualifies" for a book.
If you hunt soley to get your name in a record book you are probably part of the problem.
BTW bows with greater than 65% let off are also illegal to hunt with in "Archery Only" hunts in Idaho.