Looks like this can save both on battery and radiation.
My phone Bluetooth is anyway off so it's not going to sync anything anyway.
The watch can be pretty close to the brain while sleeping, there is no reason to have this Bluetooth radiation on every night.
Garmin watches recognize sleeping so why not automatically turning BT off while user is sleeping?
Alternately, some watches have a "do no disturb" mode. Why not turning BT off while in this mode?