Agree, as in when you turn off location on your mobile device they can still triangulate where you are using cell tower you latched to as well as the info pack about your device including MAC address. When you register your device it obtains the IMEI International Mobile Equipment Identity as part of the process.
I have also looked into the DNS aspect of the whole process and at the end of the day becoming truly “invisible” is impossible.
A burner phone is a good start. If you need to become "truly" invisible.