Even when toggled off in Control Center on an iPhone, iPad, or iPod touch running iOS 11 and later, a new support document says Bluetooth and Wi-Fi will continue to be available for AirDrop, AirPlay, Apple Pencil, Apple Watch, Location Services, and Continuity features like Handoff and Instant Hotspot.
Toggling off Bluetooth or Wi-Fi in Control Center only disconnects accessories now, rather than disabling connectivity entirely.
If Bluetooth is turned off, the iOS device can’t be connected to any Bluetooth accessories until one of these conditions is met:
While Wi-Fi is disabled, auto-join for any nearby Wi-Fi networks will also be disabled until one of these conditions is met:
iOS 11 users can still completely disable Wi-Fi and Bluetooth for all networks and devices by toggling them off in the Settings app.
Apple says users should try to keep Wi-Fi and Bluetooth turned on for the best experience on an iOS device.