The iOS 11 Control Center disconnects Wi-Fi or Bluetooth, but doesn't turn them off
The radios themselves, however, will keep humming in the background in a low-power state. As per Apple, this is done to ensure that some features can be accessed immediately:
The thing is that, even in a standby mode, the Bluetooth and Wi-fi radios are still on, and can be hacked to gain access to your handset or tablet, say security aficionados. Fret not, as Apple says it has provided a way to completely nix the radio emissions by going to Settings > Wi-Fi or Bluetooth, and turning them off via the switch. It's a bit convoluted for the average user who thinks they are toggling the radio off completely when they tap on the Control Center icon, though.