Trying to figure out why things are used in some places and others are used in other places and order of operations.

Apparently using this luxury resources all 3 levels causes a 150% reduction on overcolonization:

<SimulationDescriptor Name="RecipeIngredientEffect22" Type="RecipeIngredient">
<Modifier       TargetProperty="OverColonizationPenalties" Value="-0.5" Operation="Percent" Path="./ClassColonizedStarSystem"/>
</SimulationDescriptor>

However to do the same thing the expansionists trait does it this way:
<SimulationDescriptor Name="FactionTraitExpansionists2"    Type="FactionTrait">
<Modifier TargetProperty="OverColonizationPenaltiesReduction"      Value="-0.5"    Operation="Addition"  Path="ClassEmpire"/>
</SimulationDescriptor>

And the code they both seem to apply to is this:

<Modifier       TargetProperty="OverColonizationConstant"     Operation="Addition"             Value="10"       />
<BinaryModifier TargetProperty="OverColonizationMalus"        Operation="Addition"             Left="$(OverColonizationThreshold)" BinaryOperation="Subtraction"    Right="$(ColonizedStarSystemStateColonyCount)" />
<Modifier       TargetProperty="OverColonizationMalus"        Operation="Percent"              Value="$(OverColonizationPenaltiesReduction)"       />
<BinaryModifier TargetProperty="OverColonizationPenalties"    Operation="Addition"             Left="$(OverColonizationMalus)"     BinaryOperation="Multiplication" Right="$(OverColonizationConstant)" Path="ClassEmpire/ClassColonizedStarSystem" />

Were they applied differently to the different values for a reason? For some reason I'm having a hard time parsing this.

To be specific my goal in asking this is not just to learn XML better but to hopefully make all of the OverColonizationPenaltiesReduction effects multiplicative instead of additive.