Shoulder dimpling is caused by overlubrication, either during the lube step, or from accumulation inside the sizing die shoulder. It does no harm either way as long as the metal is not actually folded over from LOTS of lube. Firing straightens it out no problem.
You can avoid these cosmetic dimples by using less lube, and by the small extra step of wiping off the neck/shoulder area after lubing. Or, you can change lubes and avoid the buildup in the sizing die.
Imperial Sizing wax is good, as are several others that eliminate the degreasing of sized cases.
HTH
John