Yes, actually.

In fact, on a percentage of speed, a heavier rider will experience a larger % increase in speed than a lighter rider would.

edit: hrmm. Now I'm not so sure lol. I worked out a couple scenarios using bikecalculator.com. 150lb rider gained 6% going up a grade losing 10lbs. 200lb rider gained 5% speed going up the same grade losing the same weight. I'm a bit confused by this if I'm being honest