Answer

The short answer is no.

EFM8 families have a 32-bit unique identifier (UID) or a 128-bit universally unique identifier (UUID).

The number of unique combinations for a 32-bit number is 2^32 (4,294,967,296). Once Silicon Labs manufactures this quantity of a single MCU part number, the ID will no longer be unique.

The number of unique combinations for a 128-bit number is 2^128 (340,282,366,920,938,463,463,374,607,431,768,211,456). Once Silicon Labs manufactures this quantity of a single MCU part number, the ID will no longer be unique. Although this number is not guaranteed to be unique for all time, this UUID is considered "practically unique" because it is not likely that this quantity of a single MCU part number will ever be manufactured.

The only way to guarantee uniqueness would be to use your own process/serial number.