“Why do you think that they can track you when it is turned off?”
They’ve been able to do that for a long time. A few years ago someone — I think it was Stossel, but not sure — did an expose on this. Cell turned off, and I think that the battery gone, later Google provided a printout of every place the person had gone. It even made assumptions that the person had stepped out of the car at a specific time. (It was true; he had.) Some other gizmo in the phone does this.
I cannot speak for all of companies, but this is not the cases for the companies that I worked for over the last 20 years. The ICs are designed with a simple connection between itself and the power button. The phone is not even in standby. What it is waiting for is a closed circuit which energizes the main IC, that in turn boots the phone. I worked for a Motorola and Qualcomm, and they didn’t do it because it would kill their battery life. Qualcomm is the primary chipset for 100s of millions of phones around the world. Others like, Apple, make their own chipset.