If you have a 30" draw and shoot a 6.5" brace the arrow is on the string for 23.5".
If you have a 26.5" draw and shoot a 6.5" brace the arrow is on the string for 20".
The negative effect that poor shooting form, or a shaky hand or arm, or from making a shot from a difficult angle while in a tree stand, would be magnified the longer the arrow stays on the string. That is why it is said that a short draw archer can get away with shooting a shorter brace than a long draw archer.