The function of this command and how it works within the device is described on this page of Source . Android Lock and unlock the bootloader.
Is this question a follow on from FP5 stucks in boatloader mode - #3 by aibd and is it the same phone? and has it remained unlocked since?
If yes the real hazard of locking is described (answered) Install /e/ on FP5 with newer Security Patches - #13 by aibd.