I have noted, also, that when I shoot my horsebow with fingers, I don't get the speed that I see when shooting with the ring.
The ring, actually, works like a caliper release. When you get it right (the release) the speed difference is markedly different. A good, clean release really shows in speed.
If one had a longbow, with no arrow shelf, it may be possible to use a ring with that style longbow. YOu would have to shoot off the right side of the riser, though. (for a dexterous person)