The purpose is to avoid creation of lists that contain negative rates or in accidental confusion with list of fluxes. Instances are usually automatically created from data
ConstantOutFluxRateList_by_PoolName
in their signature:by_PoolIndex,ConstantOutFluxRateList_by_PoolName,ANY,ANY-method
ConstLinDecompOp,missing,ConstantInternalFluxRateList_by_PoolName,ConstantOutFluxRateList_by_PoolName,missing,character-method