With all due respect, this statement is quite inaccurate. Some history and context is in order, at least given my own personal and professional experience; indeed, I started using AutoCAD back in version. 2.6 (mid 80s), taught courses in digital design computation for more than 20 years. I’ve been in effect addressing these topics, using both these software, AutoCAD and SketchUp (since beta of version 1).
At one point, late 80s and early 90s, Autodesk bought a company that had developed a 3D engine that ran parallel to AutoCAD (one had to Import into AutoCAD the data. They later provided an add-on, ca. version 12, called Advanced Modeling Extension, which incorporated Constructive Solid Geometry - hierarchical 3D structures, linked together via solid-modeling (a.k.a. Boolean) operations. Upon version 14 they changed CSG to B-Rep (Boundary Representation) using Spatial’s engine… Today , and for quite a while, AutoCAD has some NURBS modeling capability but fundamentally Mesh Modeling (i.e. 3D surfacing) and of course Solids.
Obviously, one does not have to “like” how AutoCAD’s UX works, what is its “3D-ness”; that’s a personal preference. But, that 3D is and has been there is unquestionable.