You're right, it is but one small factor of a long list of factors that add to or detract from forgiveness of a bow. However, all other things being exactly the same the shorter brace height bow will be less forgiving than the bow with the longer brace height because the bow will move just a little bit more before the arrow leaves the string.

I know this would be virtually impossible to achieve but that's the theory. The quicker an arrow gets off the string the less a person can move the arrow around.

Riser design, riser material, limb pocket desicn, limb material, split or solid limbs, length of limbs, weight of the bow, string material, cam design, draw force curve, arrows used, head weight, total arrow weight etc...etc...etc... all play a part in how forgiving a bow is.