No doubt to me that a fully extended arm is detrimental to productive shooting. If you're resisting something with a fully extended arm, your arm is less stable. You shouldn't need to fully extend the arm to be at full draw. You should be drawing it with your string hand, thus we call it drawing, and you should be holding the weight with your back muscles. If your arm is slightly bent, it'll be stronger and function as a unit. If you've ever tried to push a car that won't start, notice how you push. No doubt you push with your legs, but your arms are against the car in what manner? Most likely they'd be bent. Why? because they're stronger, more stable that way.

God bless,
Brandan