> if the interface elements have strong information hierarchy

...but that's an example of a UX/usability matter that can be assessed objectively and non-subjectively.

I disagree.

Is 16 px or 14 px a better font-size value for a subheading, in a hypothetical layout? Immediately that kind of decision, where both options are objectively good for 12 px paragraph text, suddenly becomes an issue of taste that cannot be evaluated crudely by an algorithm.