I am not sure if this should really prevent the creation of a 3D Mesh, it says only “full 3D Model” I also guess that at least a minimalistic model is needed because of the camera parallax effect which comes from your different positions and the camera lens curvature which is (maybe) less important. Otherwise, your 2D Orthophoto would be strange as the one from google. When you ever had a closer look at the google earth / maps images, you will see that the image is not perfectly from top.