Problem is that the bluetooth is visible to anyone within the range. This is a concern and is an increase of risk. Your selling point is that no one have to know that one has a smartlock. But this discoverable bluetooth with the Nuki name is a BIG giveaway. Please give the user option to hide or advertise. Could you build in an option to hide or change the Bluetooth name.
Any BLE device needs to advertise in order to be reachable. You can not change that.
Changing the name would in theory be possible, but does not really help much as anyone can still connect and search for the characteristics & services the Smart Lock offers (see BLE API for more details).