This has been fixed and was released in Matplotlib v3.9.0, so that the 3D axis limits no longer have extra padding added. So 2D objects down on the axis panes will now be flush against them. See for example this gallery plot: https://matplotlib.org/stable/gallery/mplot3d/contourf3d_2.html#sphx-glr-gallery-mplot3d-contourf3d-2-py