Among other things yes. But give Cutler a 100 lbs barbell instead of that 50 lbs barbell, he would be 'lifting more weight' but wouldn't necessarily be training his biceps any harder.
I agree with Scott Abel that a lot of bodybuilders, even though they get stronger over time, use less training weight over time, simply because they've mastered the contracting of muscles better.
(of course the drug intake will likely also grow over time!)