You might also want to discuss Fitt’s law. Difference between a diagram (Tufte) and a GUI is that we only look at a diagram, but a GUI we interact with, which means we need to ensure people can actually click/tap/select the element of interest. Higher density makes that harder.
I was with you until the last sentence. Removing borders makes it harder. Not being able to see the actual area of a clickable target makes it harder. I never had trouble knowing what to click in the early 2000’s, when UI was ostensibly more dense.
