[dnanian]

Dan, it made the copy as it should. It didn't "pretend" to back up. (Feel free to send me the log to verify.)

If the boot manager doesn't see it, it may have had the wrong partitioning scheme, or High Sierra had never been *installed* to the system (it had been restored, or copied from elsewhere) and thus the BIOS doesn't have APFS capability, even if the *system* does.