Lumped masses should not be a part of "total mass" or, there should be another system parameter that clearly conveys the mass of all the actual geometry being analyzed. Including lumped masses in any optimization designed to minimize "total mass" messes up the ability of the optimizer to successfully optimize structure.
Think of designing two small brackets that are being designed to support some heavy object between them. The heavy object gets designed as a lumped mass and it can easily weigh 10X what each of the brackets weigh. The optimizer "sees" very little change in "total mass" even when making large changes to dimensions of the bracket.