I would assume it's just using less weight more efficiently but exactly how does it help the bow?
These two about sums it up. I have a straight 30" front stab with 1" straight quick disconnect and a 30" front stab with 1" 10 degree down quick disconnect. Both tried on one bow, the 10 degree does make a nice difference. Just now trying 10 degree down on second bow and results are that of being more stable. Like ron noted something of centering bow mass in gravity terms.....pendulum effect,...the weight wants to settle to the bottom of the radius made by the distance in offset between the point that the stab attaches to the bow and the lower position of the weight at the end of the stab.
it helps by dynamically putting the bow in a vertical position.
one of the fairly little known facts about down stabs, is that they can be offset to correct a slight natural cant because gravity will try to pull the weight to the farthest low position attainable. when the stab is slightly off set, the weight is not at the bottom of the above mentioned radius, so gravity tries to correct the cant by pulling the weight to the lowest possible position.
Actually it acts like less weight. When I put the 20 down on my bow sat straight up after the shot. I added more weight to get it to roll forward again like I want it to. It makes since if you think about it, by angling down the weight comes closer to the bow and changes the balance back to the shooter.By lowering the angle you increase the weights leverage so it acts like you have more weight.