If drum brakes are not re-centered during adjustment, they are not properly adjusted.

"...gradually move the adjuster until you have a good deal of friction on the wheel, but it is still able to turn with some effort. The next step is very important. Either with a helper in the car or by doing it yourself, hit the brake pedal hard a few times. This will re-center the shoes and you will find that a good deal of the friction will be eliminated. Re-adjust the shoes until you achieve slightly less friction than the last time. Re-apply the brake a few times. When the shoes are adjusted properly, the friction against the wheel will not be altered after the brake pedal is (hit hard and re-centered). The adjustment is correct when the shoes rub lightly against the drum..."

From:
http://www.hemmings.com/mus/stories/2006/10/01/hmn_q_and_a1.html