Fastboot mode will give you the opportunity to reinstall Install /e/OS on a Murena Murena One - “one”. Notice how the process involves fastboot only.
Fastboot mode might be seen as a “communication channel” – nothing will happen, but the device is open to fastboot commands from your PC.
When starting working with fastboot always start with the command
fastboot devices
and ensure you get a response from the device (it will identify itself) before you start the intended task.
If in doubt, the command
fastboot getvar lock_state
should tell you whether the device is locked.