Servos designed to take greater than "standard" throw range... fine, go ahead and use the capability. A Standard servo as used by the average beginner (the ones that come with the average 4 to 6 ch radio system...) is not designed to handle the added travel of exceeding "100%" ATV.

the geometry of the normal pushrod system mathematically can be reduced to a series of levers and fulcrums. When you mechanically decrease throw, rather than using ATV, you increase the effective servo power for the same deflection angle. You also increase the effective precision of control surface movement.

Do a few weight lifting experiments with a servo... tie a 40 oz weight one inch out on the servo arm and then make the servo lift the weight. Move that weight out to 2 inches, and try to get the same servo to lift it the same distance as before. Try 1/2 the weight... then 1/4. (with a "standard" 45 to 52 in-oz servo, only the first and last lifts will succeed.)