The raw image support has nothing to do with silicon bring-up. That is an option for a userspace tool running in macOS recovery mode. At that point you're well

The raw image support has nothing to do with silicon bring-up. That is an option for a userspace tool running in macOS recovery mode. At that point you're well past silicon bring-up. I don't know why people keep conflating those two things... it doesn't make any sense whatsoever. Silicon bring-up would happen via iBoot on completely unlocked chips (no secureboot fuses). The raw image mode was added for us. Apple has absolutely zero use for such an option.