Right ... and conversely, you can throw a ball through a brick wall, but like Rob Johnson, you can't find your receiver fast enough and you get sacked or like Kyle Boller and you overthrow your receiver by 20 yards ... I'll take field smarts, vision, decision making and accuracy over a strong arm.
But back to original point ... you are what you are, and arm strength is part physical and part mechanical, so to a large extent, either you have it or you don't.