I took a visualization course and to paraphrase the prof. you have a 3d object projected onto a 2d (display) plane and reasoning about depth gives additional mental load, not to mention occlusion. You have to interact with the model a lot to get a view you want. The course was based on old papers about UX with a dash of cognitive science, so take it with a grain of salt.

Yup, this. There's almost always a way to represent the data that allows clearer interpretation.

He is umm. very opinionated. Its kind of like saying why need two dimensions, surely a 1D vector is good enough..