Advanced optimus

Can someone explain to me what the auto mode in Nvidia control panel does? Because what I understand is that it should use the iGPU when it's not plugged in and not playing games, and when I plug it in and play a game, it should switch to the dGPU. And when I tried to play a game and open the Nvidia control panel, it says iGPU, but in task manager, the dGPU is working. So why does the Nvidia control panel make the display work on the iGPU and not the dGPU?