True based on my experience.. When I talked to my tire dealer (very knowledgeable) I initially told them to mount, but not balance the tires since they didn't have the lugcentric adapter.. and I was going to take it to the Toyota dealer to get them balanced.

He was very knowledgeable about the problem and asked that I give him a shot at balancing.. They got them perfect..

They check how the tire initally lines up on the balancer (not sure how they do this, maybe check wheel runout with a dial gauge) and after balancing, move the tire (maybe 90 or 180 degrees on the balancer and re check... if they were centered properly they will still be in balance.. if not, they do it all over again..