3D can have a lot more to do with math and geometry to make things successfully, at least basic things anyway, than it would be for somebody without a mind that can render form in a 2D environment to actually look like what it should look like based on its 3D shape. You know a mug is a hollow cylinder with a cap on the bottom and a handle. If you can use some simple tools to make that in 3D then add a simple color and lightsource to it, it will look great - Hey, I recognize that to be a mug, good job! But doing so in 2D, if you're not trying to make a flat looking piece, you would have to know how to present that object to have a mocked up depth by way of shading, shadow, etc, without the use of that Z axis. This is just a very basic example, but it can be applied to different things.
One can have a good understanding of things in a 3-dimensional sense and not be an artist. They could mimic something they see on their desk and eventually create a 3D model of it exactly just by measuring it and re-creating one piece at a time, but if they went and tried to draw it on a page, they'd be at a loss if they tried to make it look nearly as nice looking without the automated processes the 3D program would do for them, such as adding lighting, shading, reflection, perspective, etc etc etc. These are things you much teach your brain how to recognize and recreate in a 2D sense while drawing.