Are you sure? I know they keep some WiFi on, but I didn't think there was much location value in bluetooth signals because most bluetooth devices people use are portable (headphones, cars, etc.)
Actually yes, I did investigate that. Can post a screenshot.
Did you also disable that setting under the "location" submenu, which explicitly says it works even if bluetooth is off?
Not that this is good design, mind you, but if you turned both settings off and still say BT activity, then that is much different.
If you do that, it will disable it. Yes, it's a well hidden option deep in the menu.