Apple quietly changed the behaviour of the Wi-Fi and Bluetooth toggles in Control Center in iOS 11. Instead of switching the two radios off, toggling the Wi-Fi and Bluetooth switch to off only led to the iOS device disconnecting from all connected Wi-Fi networks and devices.
Apple was criticised for this change when this change was first discovered by users. Now, with the iOS 11.2 beta 3 update, Apple shows a pop up to explain the new functionality of the Bluetooth and Wi-Fi toggles in Control Center. The pop-up makes it clear that toggling Wi-Fi/Bluetooth off will only lead to your iPhone or iPad being temporarily disconnected until tomorrow from the current Wi-Fi network and connected Bluetooth devices.
The two radios will continue to be available for core iOS features like AirDrop, improved location accuracy, Handoff, and more. If you need to completely disable Wi-Fi and Bluetooth on your iOS device, you need to do so from the Settings menu.
Additionally, when turned off, the background of the Wi-Fi/Bluetooth toggles in Control Center will feature a white background to depict this change.
As mentioned, toggling Wi-Fi and Bluetooth off from the Control Center only disables certain features of the two radios temporarily. While the pop-up from Apple says that Wi-Fi/Bluetooth will automatically turn on tomorrow which is 5 a.m. as per Apple’s definition. The ‘tomorrow’ scenario also has a few other conditions as well. If you go to a different location, your iPhone/iPad will automatically connect to a known Wi-Fi network there. Similarly, if you restart your iOS device, it will automatically reconnect to a known Wi-Fi network even if you previously disconnected it from the Control Center. The same conditions also apply for Bluetooth.
A lot of core iOS features like Continuity, Handoff and improved location prediction rely on Wi-Fi and Bluetooth which is likely why Apple has now made it more difficult for users to completely turn these radios off. Technological improvements mean that the Wi-Fi and Bluetooth radios barely have an impact on battery life so most users are not going to be aware of them being always on and silently working in the background.