What the "locally administered" bit actually guarantees

Every MAC address has a bit reserved to distinguish addresses assigned globally by a hardware vendor (drawn from that vendor's IEEE-registered OUI block) from ones assigned locally, ad hoc, for a specific purpose. This tool always sets that bit and always clears the multicast bit, which means every address it generates is guaranteed, by construction, never to collide with a real factory-assigned NIC address — it's structurally impossible for a random locally-administered address to also be a valid globally-assigned one. That's different from just picking random bytes for all 6 octets, which could, in principle, land on a real vendor's OUI prefix.

This is exactly what virtualization platforms do internally when assigning MACs to VM and container network interfaces, which is the main practical use case here — generating one by hand when a hypervisor's auto-assignment isn't available or predictable enough for a test setup.