Preventing BLE reconnection after pairing. Single-use connection.

Ahh, getAddress is always the hard-coded address, not the one you set with setAddress. Use something like NRF connect on a phone to scan for devices to see the real address.

You want random addresses - there's a bit of info here: http://www.espruino.com/About+Bluetooth+LE#connecting-puck-as-central-

I just tried here and it works fine - but you do need to disconnect from BLE first with NRF.disconnect() before the changes take effect I imagine.

Is there a command to reset this back to factory default?

No - you can either reset() the device, or do something like :

NRF.setAdvertising({},{name:"Puck.js "+NRF.getAddress().substr(-5).replace(":","")});