This is correct. As I understand it, Apple have a database of product information and if you do wipe your SPI flash, it will be restored by phoning home during

This is correct. As I understand it, Apple have a database of product information and if you do wipe your SPI flash, it will be restored by phoning home during the DFU restore process (by identifying your machine based on its fused in ECID), though I've yet to try this. So it should be in fact fully recoverable. This information is in the system configuration area, and gets inserted into the device tree template by iBoot2. You can see the template DT and what sysconfig entries it pulls data from if you extract it from an OS restore image instead of looking at the runtime DT with ioreg.