That’s the point. It doesn’t. It just ensures the public expenditure is ugly.
If it’s Design-Build, the contractor will pocket the differential. If it’s Design-Bid-Build, you end up with cut and pasted designs without any design wherewithal to adress actual design.
It’s like making a regulation that all maladies are prescribed aspirin to save medical treatment costs.
who cares if it’s ugly? you can’t eat ‘ugly’. would you prefer having lovely, artistic designs soaring to the heavens when the people being overtaxes to pay for them have to eat dog food?