While the BBC micro:bit has hardware capable of allowing the device to work as a Bluetooth Low Energy (BLE) device, it only has 16k of RAM. The BLE stack alone takes up 12k RAM which means there’s not enough memory for MicroPython to support Bluetooth on a micro:bit V1.
The nRF52833 used by the micro:bit V2 has 128k of RAM, allowing Micropython to make use of the BLE stack. Currently the only implemented feature is BLE flashing, allowing a user to update the firmware on the micro:bit over Bluetooth.
At the time that this was written the Nordic DFU service is implemented, and partial flashing is currently working but in beta. The Nordic DFU service updates everything in flash and will take a (relatively) long time to complete, whereas the partial flashing service only updates the filesystem containing the user scripts.