40 fps is much much better than 30.
Every VRR user knows that.
This has nothing to do with VRR.
40 FPS on a refresh rate that divides evenly into it will be smooth without judder.
By that logic, if you have a display that supports 90hz, you can run a 45 FPS game on it and it will divide evenly and play even smoother without any judder. It just needs to divide evenly.